code: def remove_parenthesis_around_tz(cls, timestr):
          
          parenthesis = cls.TIMEZONE_PARENTHESIS.match(timestr)
          if parenthesis is not None:
              return parenthesis.group(1)
docs: get rid of parenthesis around timezone: (GMT) => GMT
  
          :return: the new string if parenthesis were found, `None` otherwise