@classmethod
def user_exists(cls, *args, **kwargs):
    """
        Return True/False if a User instance exists with the given arguments.
        Arguments are directly passed to filter() manager method.
        """
    if 'username' in kwargs:
        kwargs[cls.username_field()] = kwargs.pop('username')
    return cls.user_model().objects.filter(*args, **kwargs).count() > 0
