code: private function getConfigKeys()
      {
          if (isset($this->configKeys)) {
              return $this->configKeys;
          }
          $this->configKeys = array(
              'debug' => array(
                  // any key not found falls under 'debug'...
              ),
              'abstracter' => array(
                  'cacheMethods',
                  'collectConstants',
                  'collectMethods',
                  'objectsExclude',
                  'objectSort',
                  'useDebugInfo',
              ),
              'errorEmailer' => array(
                  'emailBacktraceDumper',
                  // 'emailFrom',
                  // 'emailFunc',
                  'emailMask',
                  'emailMin',
                  'emailThrottledSummary',
                  'emailThrottleFile',
                  'emailThrottleRead',
                  'emailThrottleWrite',
                  // 'emailTo',
                  'emailTraceMask',
              ),
              'errorHandler' => \array_keys($this->debug->errorHandler->getCfg()),
              'output' => array(
                  'addBR',
                  'css',
                  'displayListKeys',
                  'filepathCss',
                  'filepathScript',
                  'onOutput',
                  'outputAs',
                  'outputAsDefaultNonHtml',
                  'outputConstants',
                  'outputCss',
                  'outputHeaders',
                  'outputMethodDescription',
                  'outputMethods',
                  'outputScript',
              ),
          );
          return $this->configKeys;
      }
docs: get available config keys for objects
  
  @return array