Bug fix: Revert an incorrect edition on wrapper.FrameStack

[ZhiqingXiao]

Description

#2752 incorrectly removes the obligated positional parameter of self.observation(), which makes the wrapper class no longer work. This bug fix corrects it.

@arjun-kg @pseudo-rnd-thoughts @jkterry1

Type of change

Please delete options that are not relevant.

• [ +] Bug fix (non-breaking change which fixes an issue)

Screenshots

Please attach before and after screenshots of the change if applicable.

Before fix:

File ~\anaconda3\envs\py310\lib\site-packages\gym\wrappers\frame_stack.py:181, in FrameStack.step(self, action)
    176 observation, reward, terminated, truncated, info = step_api_compatibility(
    177     self.env.step(action), True
    178 )
    179 self.frames.append(observation)
    180 return step_api_compatibility(
--> 181     (self.observation(), reward, terminated, truncated, info), self.new_step_api
    182 )

TypeError: FrameStack.observation() missing 1 required positional argument: 'observation'

Checklist:

• I have run the pre-commit checks with pre-commit run --all-files (see CONTRIBUTING.md instructions to set it up)
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

[pseudo-rnd-thoughts]

Thanks for your PR, could you run the pre-commit, CONTRIBUTIONS.md in the root folder for an explanation of implementation.

[ZhiqingXiao]

Unfortunately I had difficulty in setting up the environment. I might give up.
I still suggest merge this PR even when there is a check failure, since it does not make things worse.

Detail:
I installed git and pre-commit, and executed the pre-commit command, but I encountered the error "ImportError: DLL load failed while importing _ctypes: The specified module could not be found." in the trace of "import ctypes". I checked that in that Anaconda environment both ctypes and _ctypes can be successfully imported and used, so there are something complex/weired happened. I Googled, but it seems that there are no clear solution for it.

The error message when running pre-commit run --all-files:

      File "C:\Users\Zhiqing\.cache\pre-commit\repoilsxiwyi\py_env-default\lib\site-packages\pip\_vendor\platformdirs\windows.py", line 3, in <module>
        import ctypes
      File "C:\Users\Zhiqing\anaconda3\envs\py310\lib\ctypes\__init__.py", line 8, in <module>
        from _ctypes import Union, Structure, Array
    ImportError: DLL load failed while importing _ctypes: The specified module could not be found.

[pseudo-rnd-thoughts]

Could you update it to

        return step_api_compatibility(
            (self.observation(None), reward, terminated, truncated, info),
            self.new_step_api,
        )

[ZhiqingXiao]

Could you update it to

        return step_api_compatibility(
            (self.observation(None), reward, terminated, truncated, info),
            self.new_step_api,
        )

Thanks very much. I edited accordingly. Now it passed all checks.

[pseudo-rnd-thoughts]

LGTM

[ZhiqingXiao]

Thanks.