define flow self check input
  $allowed = execute self_check_input

  if not $allowed
    bot refuse to respond
    stop

define flow self check output
  $allowed = execute self_check_output

  if not $allowed
    bot refuse to respond
    stop

define flow user query
  $answer = execute user_query
  bot $answer

define bot refuse to respond
  "I'm sorry, I can't respond to that. How can I help with questions about Eurostar?"