add null check in string with regular expression (#15233)

samples/client/echo_api/python-nextgen/openapi_client/models/default_value.py

@@ -42,6 +42,7 @@ class DefaultValue(BaseModel):
     def array_string_enum_default_validate_enum(cls, v):
         if v is None:
             return v
+
         for i in v:
             if i not in ('success', 'failure', 'unclassified'):
                 raise ValueError("each list item must be one of ('success', 'failure', 'unclassified')")

samples/client/echo_api/python-nextgen/openapi_client/models/pet.py

@@ -41,6 +41,7 @@ class Pet(BaseModel):
     def status_validate_enum(cls, v):
         if v is None:
             return v
+
         if v not in ('available', 'pending', 'sold'):
             raise ValueError("must be one of enum values ('available', 'pending', 'sold')")
         return v

samples/client/echo_api/python-nextgen/openapi_client/models/query.py

@@ -35,6 +35,7 @@ class Query(BaseModel):
     def outcomes_validate_enum(cls, v):
         if v is None:
             return v
+
         for i in v:
             if i not in ('SUCCESS', 'FAILURE', 'SKIPPED'):
                 raise ValueError("each list item must be one of ('SUCCESS', 'FAILURE', 'SKIPPED')")