<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def catch_nb_assignment(func):
 """ Wrapper to catch `nb` keyword arguments This helps catch `nb` keyword arguments and assign onto self when passed to the wrapped function. Used for callback methods when the caller may optionally have a new copy of the originally wrapped `nb` object. """


    @wraps(func)
    def wrapper(self, *args, **kwargs):
        nb = kwargs.get('nb')
        if nb:
            # Reassign if executing notebook object was replaced
            self.nb = nb
        return func(self, *args, **kwargs)

    return wrapper