'Add a new callback for this object.
Args:
callback_name (str): the name of the callback to add.
code (str): the Python code associated with this callback.
author (Character or Player, optional): the author of the callback.
valid (bool, optional): should the callback be connected?
parameters (str, optional): optional parameters.
Returns:
The callback definition that was added or None.'

def add(self, callback_name, code, author=None, valid=False, parameters=''):

    handler = type(self).script
    if handler:
        return self.format_callback(handler.add_callback(self.obj, callback_name, code, author=author, valid=valid, parameters=parameters))
