fix: codegen of Python methods

[lars-reimann]

Closes #337.

Summary of Changes

• Store instance of original class in constructor
• Call non-static methods on this instance
• Call static methods on the original class
• Normalize names of implicit parameters (always called self now)

Credit goes to @paul0314 (9001fbe, 17b961d, 2fce03c).

[github-actions]

MegaLinter status: ✅ SUCCESS

Descriptor	Linter	Files	Fixed	Errors	Elapsed time
✅ CREDENTIALS	secretlint	yes		no	2.89s
✅ GIT	git_diff	yes		no	0.01s
✅ KOTLIN	ktlint	11	0	0	21.18s

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