docs: def parse_line(self, line):
      """
      For each line we are passed, call the XML parser. Returns the
      line if we are outside one of the ignored tables, otherwise
      returns the empty string.
  
      @param line: the line of the LIGO_LW XML file to be parsed
      @type line: string
  
      @return: the line of XML passed in or the null string
      @rtype: string
      """
      self.__p.Parse(line)
      if self.__in_table:
        self.__silent = 1
      if not self.__silent:
        ret = line
      else:
        ret = ""
      if not self.__in_table:
        self.__silent = 0
      return ret