def _exc_callback_fun(self, parm) -> None:

The `def _exc_callback_fun(self, parm) -> None:` line defines a function within your class that is likely used for handling exceptions or error conditions. The `_exc_callback_fun` is a private method (indicated by the underscore prefix), so it's meant to be called internally and not intended for direct use outside of the class.

Here's an overview of what the function might do based on its signature:

1. **Arguments:** It takes one argument, `parm`, which could be any data passed when the exception occurs. This parameter can help provide context for the error handling.

2. **Return Type:** The function returns `None`, indicating that it doesn't return a value but rather handles the exception or error internally.

In the context of the provided examples, if you had something like this inside a class definition:

class MyClass:
    def __enter__(self):
        print '__enter__'
        
    def __exit__(self, exc_type, exc_value, traceback):
        if exc_type:
            self._exc_callback_fun(exc_value)
        else:
            print '__exit__ without exception'

    def _exc_callback_fun(self, parm):
        print(f"Error occurred: {parm}")
        # Do other error handling actions here
        return None

When entering a block using `with` statement, if an exception occurs during execution, the `__exit__` method would call `_exc_callback_fun` to handle the error. The `parm` argument would contain details about the raised exception.