@classmethod
def query(cls, key, value):
    """
        Builds a select query
        """
    if hasattr(cls, key) is False:
        return None
    operator = None
    if value[0] in ['!', '>', '<', '~']:
        operator = value[0]
        value = value[1:]
    cls.q = cls.filter(key, cls.cast(value), operator)
