code: def get_items(self, source=None, target=None):
          
          self._groups = self.shared_dict()
          self._target_coll = target.collection
          self._src = source
          return source.query()
docs: Get all records from source collection to add to target.
  
          :param source: Input collection
          :type source: QueryEngine
          :param target: Output collection
          :type target: QueryEngine