code: def generate_checksum(message, previous_csum=0):
      
      if message.message_type in CHECKSUM_MSG_TYPES:
          csum = compute_checksum(
              message.checksum[0],
              message.args,
              previous_csum,
          )
  
          message.checksum = (message.checksum[0], csum)
docs: Generate checksum for messages with
          CALL_REQ, CALL_REQ_CONTINUE,
          CALL_RES,CALL_RES_CONTINUE types.
  
      :param message: outgoing message
      :param previous_csum: accumulated checksum value