remove_prop_from_parent.py

>>> # See https://github.com/GoogleCloudPlatform/gcloud-python/pull/404
...
>>> from gcloud.datastore import datastore_v1_pb2 as datastore_pb
>>> 
>>> mutation = datastore_pb.Mutation()
>>> insert_auto = mutation.insert_auto_id.add()
>>> path_elt = insert_auto.key.path_element.add()
>>> path_elt.kind = 'Foo'
>>> 
>>> prop = insert_auto.property.add()
>>> prop.name = 'fooProp'
>>> 
>>> # http://stackoverflow.com/q/10998254/1068170
... 
>>> prop_parent_weak = prop._listener._parent_message_weakref
>>> prop_grandparent_weak = prop_parent_weak._listener._parent_message_weakref
>>> prop_parent_actual = prop_grandparent_weak.insert_auto_id[0]
>>> print insert_auto is prop_parent_actual
True
>>> 
>>> print mutation
insert_auto_id {
  key {
    path_element {
      kind: "Foo"
    }
  }
  property {
    name: "fooProp"
  }
}

>>> print len(prop_parent_actual.property)
1
>>> print prop_parent_actual.property[0] is prop
True
>>> prop_parent_actual.property.remove(prop)
>>> print mutation
insert_auto_id {
  key {
    path_element {
      kind: "Foo"
    }
  }
}