docs: def gets(self, keyword):
          """Return the element of the list after the given keyword as string.
  
          Parameters
          ----------
          keyword : str
              The keyword parameter to find in the list.
              Putting a colon before the keyword is optional, if no colon is
              given, it is added automatically (e.g. "keyword" will be found as
              ":keyword" in the list).
  
          Returns
          -------
          obj_str : str
              The string value corresponding to the keyword parameter
  
          Example:
              kl = KQMLList.from_string('(FAILURE :reason INVALID_PARAMETER)')
              kl.gets('reason') # 'INVALID_PARAMETER'
          """
          param = self.get(keyword)
          if param is not None:
              return safe_decode(param.string_value())
          return None