code: public void update(double timestamp, String versionName, Integer versionCode) {
  		last = timestamp;
  		total++;
  		Long countForVersionName = versionNames.get(versionName);
  		if (countForVersionName == null) {
  			countForVersionName = 0L;
  		}
  		Long countForVersionCode = versionCodes.get(versionCode);
  		if (countForVersionCode == null) {
  			countForVersionCode = 0L;
  		}
  		versionNames.put(versionName, countForVersionName + 1);
  		versionCodes.put(versionCode, countForVersionCode + 1);
  	}
docs: Initializes an event record or updates it with a subsequent event.
  @param timestamp The timestamp in seconds at which and Event occurred.
  @param versionName The Android versionName of the app when the event occurred.
  @param versionCode The Android versionCode of the app when the event occurred.