Add support for functions to be parsed by the Lightning CLI in addition to Types

[ethanwharris]

What does this PR do?

Adds support for functions (e.g. classmethods) to be provided to the CLI in addition to types.
Needed for FlashCLI where we have data modules created from clasmethods

Does your PR introduce any breaking changes ? If yes, please list them.

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[codecov]

Codecov Report

Merging #8400 (771613f) into master (b7dbcc3) will decrease coverage by 0%.
The diff coverage is 92%.

@@          Coverage Diff           @@
##           master   #8400   +/-   ##
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- Coverage      88%     88%   -0%     
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  Files         218     218           
  Lines       14401   14390   -11     
======================================
- Hits        12680   12669   -11     
  Misses       1721    1721           

[carmocca]

There are some mypy complains to address

[ethanwharris]

@carmocca Yeah, mypy wasn't picking up inspect.isclass for some reason. Fixed now 😃

[tchaton]

LGTM !

[ethanwharris]

@mauvilsa thanks for the updates 😃 I've updated the PR with the required changes, mind taking another look?