Return the inner state of the `Callback`, `minimal` or not.

def get_state(self, minimal:bool=True):
        "Return the inner state of the `Callback`, `minimal` or not."
        to_remove = ['exclude', 'not_min'] + getattr(self, 'exclude', []).copy()
        if minimal: to_remove += getattr(self, 'not_min', []).copy()
        return {k:v for k,v in self.__dict__.items() if k not in to_remove}