code: def query_yes_no(question, default="yes"):
      
      valid = {"yes": True, "y": True, "ye": True,
               "no": False, "n": False}
      if default is None:
          prompt = " [y/n] "
      elif default == "yes":
          prompt = " [Y/n] "
      elif default == "no":
          prompt = " [y/N] "
      else:
          raise ValueError("invalid default answer: '%s'" % default)
  
      while True:
          print(question + prompt)
          choice = input().lower()
          if default is not None and choice == '':
              return valid[default]
          elif choice in valid:
              return valid[choice]
          else:
              print("Please respond with 'yes' or 'no' (or 'y' or 'n').\n")
docs: Ask a yes/no question via raw_input() and return their answer.
      "question" is a string that is presented to the user.
      "default" is the presumed answer if the user just hits <Enter>.
          It must be "yes" (the default), "no" or None (meaning
          an answer is required of the user).
      The "answer" return value is True for "yes" or False for "no".