def _apply_list(self, methods):
    def call(value):
      for method in methods:
        newvalue = method(self, value)
        if newvalue is not None:
          value = newvalue
      return value
    return call
Helper to test for a generator object.
dataset/ETHPy150Open GoogleCloudPlatform/datastore-ndb-python/ndb/model.py/Property._apply_list--crossover with--dataset/ETHPy150Open AppScale/appscale/AppServer/google/appengine/ext/ndb/tasklets.py/_is_generator