code: def is_regex(string):
      
      is_regex = False
      regex_chars = ['\\', '(', '+', '^', '$']
      for c in regex_chars:
          if string.find(c) > -1:
              return is_valid_regex(string)
      return is_regex
docs: TODO: improve this!
  
      Returns True if the given string is considered a regular expression,
      False otherwise.
      It will be considered a regex if starts with a non alphabetic character
      and then correctly compiled by re.compile
  
      :param string: str