docs: def _broadcast(src_processor, src_atr_name, dest_processors, dest_atr_name, transform_function):
      """
      To be used exclusively by create_broadcast.
      A broadcast function gets an attribute on the src_processor and
      sets it (possibly under a different name) on dest_processors
      """
      value = getattr(src_processor, src_atr_name)
      value = transform_function(value)
      for d in dest_processors:
          setattr(d, dest_atr_name, value)