Python generator produces unnecessary imports to __init__.py

Is your feature request related to a problem? Please describe.

In Python, speed of imports of larger codebases is quite crucial. Therefore, minimising the number of imports makes sense. Currently the generated Python code includes every sub-module in the __init__.py (for both main module, as well as api/ and models/) sub directories).

Describe the solution you'd like

The extra imports should be an option (if we want to be backwards compatible, by default on).

Describe alternatives you've considered

My current alternative is horrifying - post-processor step which does:

	echo > X/openapi_client/__init__.py
	echo > X/openapi_client/api/__init__.py
	echo > X/openapi_client/models/__init__.py

(where X is where I'm generating them)

Additional context

By doing ^ the import speed for tools which e.g. import ApiClient and use only one API over doubled. This is for project with few api/models to boot - with more, it gets even faster (in relation).

The request concerns generated init.py files in the main package and its api/ and models/ subdirectories. Start by locating the Python generator entry point and templates that produce these files, then inspect how generator options are defined. Done means the extra imports are controlled by an option and generated output reflects both settings.