def isDescendantOf(self, other):
    if isinstance(other, Key):
      return other.isAncestorOf(self)
    raise TypeError('%s is not of type %s' % (other, Key))
boolean to see if a card is valid
dataset/ETHPy150Open datastore/datastore/datastore/core/key.py/Key.isDescendantOf--crossover with--dataset/ETHPy150Open abunsen/Paython/paython/lib/cc.py/CreditCard.is_valid