[BUG][PYTHON generator leaves out import statments when a model name suffix is given

Bug Report Checklist

• [ X] Have you provided a full/minimal spec to reproduce the issue?
• [ X] Have you validated the input using an OpenAPI validator (example)?
• [ X] Have you tested with the latest master to confirm the issue still exists?
• [ X] Have you searched for related issues/PRs?
• [ X] What's the actual output vs expected output?
• [Optional] Sponsorship to speed up the bug fix or feature request (example)

Description

The openapi-generator is creating import statements and documentation that have duplicate "modelNameSuffix" references in the class name and in the file name. As an example:

• from sales_openapi.model.error_response_dto_dto import ErrorResponseDtoDto

openapi-generator version

5.1.0 This is a regression from 4.3.1.

OpenAPI declaration file content or url

https://gist.github.com/ben5448/40aa828072214fd2e490708985debfb8

Command line used for generation

Using the 5.1 generator docker image from: "docker pull openapitools/openapi-generator-cli"

docker run --rm -v ${PWD}:/local openapitools/openapi-generator-cli:v5.1.0 generate -i /local/test.yaml -g python -o /local --model-name-suffix Dto

Steps to reproduce

Run the docker command above on the yaml file provided in gist.github.com.

Examine the generated file openapi_client/model/foo_schema_dto.py. The lazy_import function will be:

def lazy_import():
    FooBSchemaDto
    FooSchemaAllOfDto

Using the same command line except remove the model-name-suffix will generate a correct lazy_import() function like this:

Note: The filename ends in _dto_dto and the imported class name ends in DtoDto.

Note: Running the openapi-generator-cli command without a model-name-suffix will generate a working set of files. However, the maven wrapper around the openapi generator defaults to a modelNameSuffix of "Dto" when no suffix is specified. The interaction between the maven wrapper and openapi generator always generates errant code.

Related issues/PRs

Suggest a fix/enhancement

Start with the OpenAPI declaration in the linked gist and reproduce the issue using the provided openapi-generator-cli:v5.1.0 Docker command with --model-name-suffix Dto. Compare generated openapi_client/model/foo_schema_dto.py and its lazy_import function with output generated without the suffix; done means imports, class names, documentation, and filenames contain the suffix only once and the generated code works.