code: def set_line_str(self, line_str):
          
          if not self.from_string:
              raise ValueError("can't set line_str for LogEvent created from "
                               "system.profile documents.")
  
          if line_str != self._line_str:
              self._line_str = line_str.rstrip()
              self._reset()
docs: Set line_str.
  
          Line_str is only writeable if LogEvent was created from a string,
          not from a system.profile documents.