code: function Notification(icon) {
  
      if (util.isNullOrUndefined(icon)) {
          throw new IllegalArgumentException();
      }
  
      this.mTitle = null;
      this.mBody = null;
      this.mIcon = icon;
      this.mSound = "default"; // the only currently supported value
      this.mBadge = null;
      this.mTag = null;
      this.mColor = null;
      this.mClickAction = null;
      this.mBodyLocKey = null;
      this.mBodyLocArgs = null; // array
      this.mTitleLocKey = null;
      this.mTitleLocArgs = null; // array
  
      this.mBuilded = false;
  }
docs: FCM message notification part.
  
  <p>
  Instances of this class should be immutable. In order to accomplish, build method
  must be called lastly. {@link #build}. Examples:
  
  <pre><code>
  var Notification = require('node-xcs').Notification;
  </pre></code>
  
  <strong>Simplest notification:</strong>
  <pre><code>
  var notification = new Notification("ic_launcher").build();
  </pre></code>
  
  <strong>Notification with optional attributes:</strong>
  <pre><code>
  var notification = new Notification("ic_launcher")
  .title("Hello world!")
  .body("Here is a more detailed description")
  .build();
  </pre></code>