code: def _IsIdentifier(cls, string):
      
      return (
          string and not string[0].isdigit() and
          all(character.isalnum() or character == '_' for character in string))
docs: Checks if a string contains an identifier.
  
      Args:
        string (str): string to check.
  
      Returns:
        bool: True if the string contains an identifier, False otherwise.