lib/utils.js
function (obj) {
    if (obj.file && obj.file.data) {
      return obj.file.data instanceof EventEmitter;
    }
    return false;
  }
function (obj) {
    if (obj.file && obj.file.data) {
      return obj.file.data instanceof EventEmitter;
    }
    return false;
  }
Determine if file data is a derivative of EventEmitter class.
https://nodejs.org/api/events.html#events_events