code: public function trace()
      {
          if (!$this->cfg['collect']) {
              return;
          }
          $args = \func_get_args();
          $meta = $this->internal->getMetaVals(
              $args,
              array(
                  'caption' => 'trace',
                  'channel' => $this->cfg['channel'],
                  'columns' => array('file','line','function'),
              )
          );
          $backtrace = $this->errorHandler->backtrace();
          // toss "internal" frames
          for ($i = 1, $count = \count($backtrace)-1; $i < $count; $i++) {
              $frame = $backtrace[$i];
              $function = isset($frame['function']) ? $frame['function'] : '';
              if (!\preg_match('/^'.\preg_quote(__CLASS__).'(::|->)/', $function)) {
                  break;
              }
          }
          $backtrace = \array_slice($backtrace, $i-1);
          // keep the calling file & line, but toss ->trace or ::_trace
          unset($backtrace[0]['function']);
          $this->appendLog('trace', array($backtrace), $meta);
      }
docs: Log a stack trace
  
  @return void