Add polymorphism support for python (#6208)

* Add polymorphism support for python

* Update api_client

* Remove leading spaces

* Bugfix

* Catch case where swagger_types is none but get_real_child_model is defined

modules/swagger-codegen/src/main/java/io/swagger/codegen/languages/PythonClientCodegen.java

@@ -41,7 +41,7 @@ public class PythonClientCodegen extends DefaultCodegen implements CodegenConfig
         // clear import mapping (from default generator) as python does not use it
         // at the moment
         importMapping.clear();
-        
+
         supportsInheritance = true;
         modelPackage = "models";
         apiPackage = "api";