@classmethod
def exists(cls, **kwargs):
    """
        A model with the values defined by kwargs exists in db?

        `kwargs` are mandatory.
        """
    if not kwargs:
        raise ValueError(u'`Exists` method requires at least one kwarg.')
    if len(kwargs) == 1 and cls._field_is_pk(list(kwargs.keys())[0]):
        return cls.get_field('pk').exists(list(kwargs.values())[0])
    try:
        cls.collection(**kwargs).sort(by='nosort')[0]
    except IndexError:
        return False
    else:
        return True
