code: function (res, res_obj) {
  
      // return response if exist, otherwise response might be returned 
      // AFTER some callback is done handling (i.e., response will be returned within the handler)
      if (typeof res_obj === 'string') {
          LOG.sys('replying a string: ' + res_obj);
          res.writeHead(200, {'Content-Type': 'text/plain'});                     
          res.end(res_obj);            
      }
      else {
          LOG.sys('replying a JSON: ' + JSON.stringify(res_obj));
          res.writeHead(200, {'Content-Type': 'application/json'});                     
          res.end(JSON.stringify(res_obj));        
      }
  }
docs: helper code  send back response to client