code: def main():
      
      import sys, signal
  
      def _exit():
          print("Thank you for playing Simple Mongo Query!")
          sys.exit(0)
  
      signal.signal(signal.SIGINT, lambda s, f: sys.stdout.write("\n") or _exit())
  
      while 1:
          expr = input("Enter query: ").strip()
          if not expr:
              break
          try:
              q = to_mongo(expr)
          except BadExpression as e:
              print(("Error! Cannot parse '{}'".format(e.expr)))
              continue
          print(("Result: {}".format(q)))
      _exit()
docs: Run an interactive CLI program that
      prints the output of running query() on the input string.