diff --git a/.circleci/config.yml b/.circleci/config.yml
index b610ceeb2bb..4efc24c7ba1 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -1,16 +1,135 @@
-version: 2
+version: 2.1
+commands: # a reusable command with parameters
+  command_build_and_test:
+    parameters:
+      nodeNo:
+        default: "0"
+        type: string
+    steps:
+      # Restore the dependency cache
+      - restore_cache:
+          keys:
+            # Default branch if not
+            - source-v2-{{ .Branch }}-{{ .Revision }}
+            - source-v2-{{ .Branch }}-
+            - source-v2-
+      # Machine Setup
+      #   If you break your build into multiple jobs with workflows, you will probably want to do the parts of this that are relevant in each
+      # The following `checkout` command checks out your code to your working directory. In 1.0 we did this implicitly. In 2.0 you can choose where in the course of a job your code should be checked out.
+      - checkout
+      # Prepare for artifact and test results  collection equivalent to how it was done on 1.0.
+      # In many cases you can simplify this from what is generated here.
+      # 'See docs on artifact collection here https://circleci.com/docs/2.0/artifacts/'
+      - run: mkdir -p $CIRCLE_ARTIFACTS $CIRCLE_TEST_REPORTS
+      # This is based on your 1.0 configuration file or project settings
+      - run:
+          command: sudo update-alternatives --set java /usr/lib/jvm/java-8-openjdk-amd64/jre/bin/java; sudo update-alternatives --set javac /usr/lib/jvm/java-8-openjdk-amd64/bin/javac; echo -e "export JAVA_HOME=/usr/lib/jvm/java-8-openjdk-amd64" >> $BASH_ENV
+      - run:
+          command: 'sudo docker info >/dev/null 2>&1 || sudo service docker start; '
+      - run:
+          command: |-
+            printf '127.0.0.1       petstore.swagger.io
+            ' | sudo tee -a /etc/hosts
+      #    - run: docker pull openapitools/openapi-petstore
+      #    - run: docker run -d -e OPENAPI_BASE_PATH=/v3 -e DISABLE_API_KEY=1 -e DISABLE_OAUTH=1 -p 80:8080 openapitools/openapi-petstore
+      - run: docker pull swaggerapi/petstore
+      - run: docker run --name petstore.swagger -d -e SWAGGER_HOST=http://petstore.swagger.io -e SWAGGER_BASE_PATH=/v2 -p 80:8080 swaggerapi/petstore
+      - run: docker ps -a
+      - run: sleep 30
+      - run: cat /etc/hosts
+      # Test
+      - run: mvn --no-snapshot-updates --quiet clean install -Dorg.slf4j.simpleLogger.defaultLogLevel=error
+      - run:
+          name: "Setup custom environment variables"
+          command: echo 'export CIRCLE_NODE_INDEX="<<parameters.nodeNo>>"' >> $BASH_ENV
+      - run: ./CI/circle_parallel.sh
+      # Save dependency cache
+      - save_cache:
+          key: source-v2-{{ .Branch }}-{{ .Revision }}
+          paths:
+            # This is a broad list of cache paths to include many possible development environments
+            # You can probably delete some of these entries
+            - vendor/bundle
+            - ~/virtualenvs
+            - ~/.m2
+            - ~/.ivy2
+            - ~/.sbt
+            - ~/.bundle
+            - ~/.go_workspace
+            - ~/.gradle
+            - ~/.cache/bower
+            - ".git"
+            - ~/.stack
+            - /home/circleci/OpenAPITools/openapi-generator/samples/client/petstore/haskell-http-client/.stack-work
+            - ~/R
+      # save "default" cache using the key "source-v2-"
+      - save_cache:
+          key: source-v2-
+          paths:
+            # This is a broad list of cache paths to include many possible development environments
+            # You can probably delete some of these entries
+            - vendor/bundle
+            - ~/virtualenvs
+            - ~/.m2
+            - ~/.ivy2
+            - ~/.sbt
+            - ~/.bundle
+            - ~/.go_workspace
+            - ~/.gradle
+            - ~/.cache/bower
+            - ".git"
+            - ~/.stack
+            - /home/circleci/OpenAPITools/openapi-generator/samples/client/petstore/haskell-http-client/.stack-work
+            - ~/R
+      # Teardown
+      #   If you break your build into multiple jobs with workflows, you will probably want to do the parts of this that are relevant in each
+      # Save test results
+      - store_test_results:
+          path: /tmp/circleci-test-results
+      # Save artifacts
+      - store_artifacts:
+          path: /tmp/circleci-artifacts
+      - store_artifacts:
+          path: /tmp/circleci-test-results
+  command_docker_build_and_test:
+    parameters:
+      nodeNo:
+        default: "0"
+        type: string
+    steps:
+      # Machine Setup
+      #   If you break your build into multiple jobs with workflows, you will probably want to do the parts of this that are relevant in each
+      # The following `checkout` command checks out your code to your working directory. In 1.0 we did this implicitly. In 2.0 you can choose where in the course of a job your code should be checked out.
+      - checkout
+      # Prepare for artifact and test results  collection equivalent to how it was done on 1.0.
+      # In many cases you can simplify this from what is generated here.
+      # 'See docs on artifact collection here https://circleci.com/docs/2.0/artifacts/'
+      - run: mkdir -p $CIRCLE_ARTIFACTS $CIRCLE_TEST_REPORTS
+      # This is based on your 1.0 configuration file or project settings
+      #      - run:
+      #          command: sudo update-alternatives --set java /usr/lib/jvm/java-8-openjdk-amd64/jre/bin/java; sudo update-alternatives --set javac /usr/lib/jvm/java-8-openjdk-amd64/bin/javac; echo -e "export JAVA_HOME=/usr/lib/jvm/java-8-openjdk-amd64" >> $BASH_ENV
+      #      - run:
+      # Test
+      #      - run: mvn --no-snapshot-updates --quiet clean install -Dorg.slf4j.simpleLogger.defaultLogLevel=error
+      - run:
+          name: "Setup custom environment variables"
+          command: echo 'export CIRCLE_NODE_INDEX="<<parameters.nodeNo>>"' >> $BASH_ENV
+      - run: ./CI/circle_parallel.sh
+      # Teardown
+      #   If you break your build into multiple jobs with workflows, you will probably want to do the parts of this that are relevant in each
+      # Save test results
+      - store_test_results:
+          path: /tmp/circleci-test-results
+      # Save artifacts
+      - store_artifacts:
+          path: /tmp/circleci-artifacts
+      - store_artifacts:
+          path: /tmp/circleci-test-results
 jobs:
-  build:
-    #    docker:
-    #      #- image: openapitools/openapi-generator
-    #      - image: swaggerapi/petstore
-    #        environment:
-    #          SWAGGER_HOST=http://petstore.swagger.io
-    #          SWAGGER_BASE_PATH=/v2
+  node0:
     machine:
       image: circleci/classic:latest
     working_directory: ~/OpenAPITools/openapi-generator
-    parallelism: 4
     shell: /bin/bash --login
     environment:
       CIRCLE_ARTIFACTS: /tmp/circleci-artifacts
@@ -18,85 +137,68 @@ jobs:
       DOCKER_GENERATOR_IMAGE_NAME: openapitools/openapi-generator
       DOCKER_CODEGEN_CLI_IMAGE_NAME: openapitools/openapi-generator-cli
     steps:
-    # Restore the dependency cache
-    - restore_cache:
-        keys:
-        # Default branch if not
-        - source-v2-{{ .Branch }}-{{ .Revision }}
-        - source-v2-{{ .Branch }}-
-        - source-v2-
-    # Machine Setup
-    #   If you break your build into multiple jobs with workflows, you will probably want to do the parts of this that are relevant in each
-    # The following `checkout` command checks out your code to your working directory. In 1.0 we did this implicitly. In 2.0 you can choose where in the course of a job your code should be checked out.
-    - checkout
-    # Prepare for artifact and test results  collection equivalent to how it was done on 1.0.
-    # In many cases you can simplify this from what is generated here.
-    # 'See docs on artifact collection here https://circleci.com/docs/2.0/artifacts/'
-    - run: mkdir -p $CIRCLE_ARTIFACTS $CIRCLE_TEST_REPORTS
-    # This is based on your 1.0 configuration file or project settings
-    - run:
-        command: sudo update-alternatives --set java /usr/lib/jvm/java-8-openjdk-amd64/jre/bin/java; sudo update-alternatives --set javac /usr/lib/jvm/java-8-openjdk-amd64/bin/javac; echo -e "export JAVA_HOME=/usr/lib/jvm/java-8-openjdk-amd64" >> $BASH_ENV
-    - run:
-        command: 'sudo docker info >/dev/null 2>&1 || sudo service docker start; '
-    - run:
-       command: |-
-         printf '127.0.0.1       petstore.swagger.io
-         ' | sudo tee -a /etc/hosts
-#    - run: docker pull openapitools/openapi-petstore
-#    - run: docker run -d -e OPENAPI_BASE_PATH=/v3 -e DISABLE_API_KEY=1 -e DISABLE_OAUTH=1 -p 80:8080 openapitools/openapi-petstore
-    - run: docker pull swaggerapi/petstore
-    - run: docker run --name petstore.swagger -d -e SWAGGER_HOST=http://petstore.swagger.io -e SWAGGER_BASE_PATH=/v2 -p 80:8080 swaggerapi/petstore
-    - run: docker ps -a
-    - run: sleep 30
-    - run: cat /etc/hosts
-    # Test
-    - run: mvn --no-snapshot-updates --quiet clean install -Dorg.slf4j.simpleLogger.defaultLogLevel=error
-    - run: ./CI/circle_parallel.sh 
-    # Save dependency cache
-    - save_cache:
-        key: source-v2-{{ .Branch }}-{{ .Revision }}
-        paths:
-        # This is a broad list of cache paths to include many possible development environments
-        # You can probably delete some of these entries
-        - vendor/bundle
-        - ~/virtualenvs
-        - ~/.m2
-        - ~/.ivy2
-        - ~/.sbt
-        - ~/.bundle
-        - ~/.go_workspace
-        - ~/.gradle
-        - ~/.cache/bower
-        - ".git"
-        - ~/.stack
-        - /home/circleci/OpenAPITools/openapi-generator/samples/client/petstore/haskell-http-client/.stack-work
-        - ~/R
-    # save "default" cache using the key "source-v2-"
-    - save_cache:
-        key: source-v2-
-        paths:
-        # This is a broad list of cache paths to include many possible development environments
-        # You can probably delete some of these entries
-        - vendor/bundle
-        - ~/virtualenvs
-        - ~/.m2
-        - ~/.ivy2
-        - ~/.sbt
-        - ~/.bundle
-        - ~/.go_workspace
-        - ~/.gradle
-        - ~/.cache/bower
-        - ".git"
-        - ~/.stack
-        - /home/circleci/OpenAPITools/openapi-generator/samples/client/petstore/haskell-http-client/.stack-work
-        - ~/R
-    # Teardown
-    #   If you break your build into multiple jobs with workflows, you will probably want to do the parts of this that are relevant in each
-    # Save test results
-    - store_test_results:
-        path: /tmp/circleci-test-results
-    # Save artifacts
-    - store_artifacts:
-        path: /tmp/circleci-artifacts
-    - store_artifacts:
-        path: /tmp/circleci-test-results
+      - command_build_and_test:
+          nodeNo: "0"
+  node1:
+    machine:
+      image: circleci/classic:latest
+    working_directory: ~/OpenAPITools/openapi-generator
+    shell: /bin/bash --login
+    environment:
+      CIRCLE_ARTIFACTS: /tmp/circleci-artifacts
+      CIRCLE_TEST_REPORTS: /tmp/circleci-test-results
+      DOCKER_GENERATOR_IMAGE_NAME: openapitools/openapi-generator
+      DOCKER_CODEGEN_CLI_IMAGE_NAME: openapitools/openapi-generator-cli
+    steps:
+      - command_build_and_test:
+          nodeNo: "1"
+  node2:
+    machine:
+      image: circleci/classic:latest
+    working_directory: ~/OpenAPITools/openapi-generator
+    shell: /bin/bash --login
+    environment:
+      CIRCLE_ARTIFACTS: /tmp/circleci-artifacts
+      CIRCLE_TEST_REPORTS: /tmp/circleci-test-results
+      DOCKER_GENERATOR_IMAGE_NAME: openapitools/openapi-generator
+      DOCKER_CODEGEN_CLI_IMAGE_NAME: openapitools/openapi-generator-cli
+    steps:
+      - command_build_and_test:
+          nodeNo: "2"
+  node3:
+    machine:
+      image: circleci/classic:latest
+    working_directory: ~/OpenAPITools/openapi-generator
+    shell: /bin/bash --login
+    environment:
+      CIRCLE_ARTIFACTS: /tmp/circleci-artifacts
+      CIRCLE_TEST_REPORTS: /tmp/circleci-test-results
+      DOCKER_GENERATOR_IMAGE_NAME: openapitools/openapi-generator
+      DOCKER_CODEGEN_CLI_IMAGE_NAME: openapitools/openapi-generator-cli
+    steps:
+      - checkout
+      - command_build_and_test:
+          nodeNo: "3"
+  node4:
+    docker:
+      - image: fkrull/multi-python
+    working_directory: ~/OpenAPITools/openapi-generator
+    shell: /bin/bash --login
+    environment:
+      CIRCLE_ARTIFACTS: /tmp/circleci-artifacts
+      CIRCLE_TEST_REPORTS: /tmp/circleci-test-results
+      DOCKER_GENERATOR_IMAGE_NAME: openapitools/openapi-generator
+      DOCKER_CODEGEN_CLI_IMAGE_NAME: openapitools/openapi-generator-cli
+    steps:
+      - checkout
+      - command_docker_build_and_test:
+          nodeNo: "4"
+workflows:
+  version: 2
+  build:
+    jobs:
+      - node0
+      - node1
+      - node2
+      - node3
+      - node4
\ No newline at end of file
diff --git a/CI/circle_parallel.sh b/CI/circle_parallel.sh
index 74e5f018f1b..b6e2691121a 100755
--- a/CI/circle_parallel.sh
+++ b/CI/circle_parallel.sh
@@ -11,7 +11,9 @@ export NODE_ENV=test
 
 function cleanup {
   # Show logs of 'petstore.swagger' container to troubleshoot Unit Test failures, if any.
-  docker logs petstore.swagger # container name specified in circle.yml
+  if [ "$NODE_INDEX" != "4" ]; then
+    docker logs petstore.swagger # container name specified in circle.yml
+  fi
 }
 
 trap cleanup EXIT
@@ -61,7 +63,6 @@ elif [ "$NODE_INDEX" = "3" ]; then
   pyenv install 3.6.3
   pyenv install 2.7.14
   pyenv global 3.6.3
-  python3 --version
 
   # Install node@stable (for angular 6)
   set +e
@@ -80,6 +81,20 @@ elif [ "$NODE_INDEX" = "3" ]; then
 
   mvn --no-snapshot-updates --quiet verify -Psamples.circleci.node3 -Dorg.slf4j.simpleLogger.defaultLogLevel=error
 
+elif [ "$NODE_INDEX" = "4" ]; then
+
+  echo "Running node $NODE_INDEX to test 'samples.circleci.node4' defined in pom.xml ..."
+
+  # install maven and java so we can use them to run our tests
+  apt-get update && apt-get install -y default-jdk maven sudo
+  java -version
+  export JAVA_HOME=$(readlink -f /usr/bin/java | sed "s:bin/java::")
+  echo $JAVA_HOME
+  # show os version
+  uname -a
+
+  mvn --no-snapshot-updates --quiet verify -Psamples.circleci.node4 -Dorg.slf4j.simpleLogger.defaultLogLevel=error
+
 else
   echo "Running node $NODE_INDEX to test 'samples.circleci.others' defined in pom.xml ..."
   #sudo update-java-alternatives -s java-1.7.0-openjdk-amd64
diff --git a/modules/openapi-generator/src/main/resources/python-experimental/tox.handlebars b/modules/openapi-generator/src/main/resources/python-experimental/tox.handlebars
index 5af8eb6f831..d1b68916df4 100644
--- a/modules/openapi-generator/src/main/resources/python-experimental/tox.handlebars
+++ b/modules/openapi-generator/src/main/resources/python-experimental/tox.handlebars
@@ -1,5 +1,5 @@
 [tox]
-envlist = py3
+envlist = py39
 
 [testenv]
 deps=-r{toxinidir}/requirements.txt
diff --git a/pom.xml b/pom.xml
index 0dd62e012c4..06f87b9cb43 100644
--- a/pom.xml
+++ b/pom.xml
@@ -1285,7 +1285,6 @@
                 <!-- clients -->
                 <module>samples/client/petstore/python</module>
                 <module>samples/client/petstore/python_disallowAdditionalPropertiesIfNotPresent</module>
-                <module>samples/openapi3/client/petstore/python</module>
                 <!--<module>samples/openapi3/client/petstore/python-legacy</module>-->
                 <!-- TODO comment out below when the test for typescript-nestjs is ready
                 <module>samples/client/petstore/typescript-nestjs-v6-provided-in-root</module>-->
@@ -1316,6 +1315,21 @@
                 <module>samples/client/petstore/javascript-promise-es6</module>
             </modules>
         </profile>
+        <!-- node 4 tests in CircleCI -->
+        <profile>
+            <id>samples.circleci.node4</id>
+            <activation>
+                <property>
+                    <name>env</name>
+                    <value>samples.circleci.node4</value>
+                </property>
+            </activation>
+            <modules>
+                <!-- python clients which don't need the server running -->
+                <module>samples/openapi3/client/petstore/python</module>
+                <module>samples/openapi3/client/petstore/python-experimental</module>
+            </modules>
+        </profile>
         <!-- other tests in CircleCI -->
         <profile>
             <id>samples.circleci.others</id>
diff --git a/samples/openapi3/client/petstore/python-experimental/pom.xml b/samples/openapi3/client/petstore/python-experimental/pom.xml
new file mode 100644
index 00000000000..7e737c36111
--- /dev/null
+++ b/samples/openapi3/client/petstore/python-experimental/pom.xml
@@ -0,0 +1,46 @@
+<project>
+    <modelVersion>4.0.0</modelVersion>
+    <groupId>org.openapitools</groupId>
+    <artifactId>PythonExperimentalOAS3PetstoreTests</artifactId>
+    <packaging>pom</packaging>
+    <version>1.0-SNAPSHOT</version>
+    <name>Python Experimental OpenAPI3 Petstore Client</name>
+    <build>
+        <plugins>
+            <plugin>
+                <artifactId>maven-dependency-plugin</artifactId>
+                <executions>
+                    <execution>
+                        <phase>package</phase>
+                        <goals>
+                            <goal>copy-dependencies</goal>
+                        </goals>
+                        <configuration>
+                            <outputDirectory>${project.build.directory}</outputDirectory>
+                        </configuration>
+                    </execution>
+                </executions>
+            </plugin>
+            <plugin>
+                <groupId>org.codehaus.mojo</groupId>
+                <artifactId>exec-maven-plugin</artifactId>
+                <version>1.2.1</version>
+                <executions>
+                    <execution>
+                        <id>test</id>
+                        <phase>integration-test</phase>
+                        <goals>
+                            <goal>exec</goal>
+                        </goals>
+                        <configuration>
+                            <executable>make</executable>
+                            <arguments>
+                                <argument>test</argument>
+                            </arguments>
+                        </configuration>
+                    </execution>
+                </executions>
+            </plugin>
+        </plugins>
+    </build>
+</project>
\ No newline at end of file
diff --git a/samples/openapi3/client/petstore/python-experimental/tox.ini b/samples/openapi3/client/petstore/python-experimental/tox.ini
index 8989fc3c4d9..ef7cec358ca 100644
--- a/samples/openapi3/client/petstore/python-experimental/tox.ini
+++ b/samples/openapi3/client/petstore/python-experimental/tox.ini
@@ -1,5 +1,5 @@
 [tox]
-envlist = py3
+envlist = py39
 
 [testenv]
 deps=-r{toxinidir}/requirements.txt