code: def set_username_prompt(self, regex=None):
          
          if regex is None:
              self.manual_user_re = regex
          else:
              self.manual_user_re = to_regexs(regex)
docs: Defines a pattern that is used to monitor the response of the
          connected host for a username prompt.
  
          :type  regex: RegEx
          :param regex: The pattern that, when matched, causes an error.