[Refactor] Address warnings / errors for locally created methods

[JosuaCarl]

Description

When I try to use code with method creation within methods, the warning

WARNING:root:
--- 1 warning(s) were found for page '/' in variable '_' ---

• Warning 1: button.on_action: print_something is not a function.

---

/.../lib/python3.12/site-packages/taipy/gui/gui.py:1502: TaipyGuiWarning: on_action(): 'print_something' is not a valid function.
_warn(f"on_action(): '{action}' is not a valid function.")

is raised.

Example:

in_str = "things!"
out_str = ""
def create_x( name:str ):
    def print_something( state, *args, something:str=name ):
        state.out_str =  f"{something} {state.in_str}"
    tgb.input( "{in_str}" )
    tgb.button( "Printer of something", on_action=print_something )
    tgb.text( "{out_str}" )

with tgb.Page() as root:
    create_x( name="Awsome" )

gui = Gui(page=root)

if __name__ == "__main__":
    gui.run(port=4999)

What does however work is, if I replace the function with a lamba statement, like:

tgb.button( "Printer of something", on_action=lambda state, id, payload: print_something( state ) )

The workaround is absolutely sufficient, but I am curious whether this could be addressed in a future release and why the lambda statement does not produce any error.

Acceptance Criteria

• Any new code is covered by a unit tested.
• Check code coverage is at least 90%.

Code of Conduct

• I have checked the existing issues.
• I am willing to work on this issue (optional)