code: def _collection(self, key):
      '''Returns the namespace collection for `key`.'''
      collection = str(key.path)
      if not collection in self._items:
        self._items[collection] = dict()
      return self._items[collectionf _collection(self, key):
      '''Returns the namespace collection for `key`.'''
      collection = str(key.path)
      if not collection in self._items:
        self._items[collection] = dict()
      return self._items[collection]
docs: Returns the namespace collection for `key`.