docs: function KernelFuncParser(importer) {
      LinuxPerfParser.call(this, importer);
  
      importer.registerEventHandler('graph_ent',
          KernelFuncParser.prototype.traceKernelFuncEnterEvent.
              bind(this));
      importer.registerEventHandler('graph_ret',
          KernelFuncParser.prototype.traceKernelFuncReturnEvent.
              bind(this));
  
      this.model_ = importer.model_;
      this.ppids_ = {};
    }