code: def _batched_op_msg(
          operation, command, docs, check_keys, ack, opts, ctx):
      
      buf = StringIO()
  
      # Save space for message length and request id
      buf.write(_ZERO_64)
      # responseTo, opCode
      buf.write(b"\x00\x00\x00\x00\xdd\x07\x00\x00")
  
      to_send, length = _batched_op_msg_impl(
          operation, command, docs, check_keys, ack, opts, ctx, buf)
  
      # Header - request id and message length
      buf.seek(4)
      request_id = _randint()
      buf.write(_pack_int(request_id))
      buf.seek(0)
      buf.write(_pack_int(length))
  
      return request_id, buf.getvalue(), to_send
docs: OP_MSG implementation entry point.