code: public GCMMessage withData(java.util.Map<String, String> data) {
          setData(data);
          return this;
      }
docs: The data payload used for a silent push. This payload is added to the notifications' data.pinpoint.jsonBody'
  object
  
  @param data
  The data payload used for a silent push. This payload is added to the notifications'
  data.pinpoint.jsonBody' object
  @return Returns a reference to this object so that method calls can be chained together.