code: public static boolean showInstallPrompt(@NonNull Activity activity, int requestCode, @Nullable String referrer) {
          String installReferrerString = Defines.Jsonkey.IsFullAppConv.getKey() + "=true&" + referrer;
          return InstantAppUtil.doShowInstallPrompt(activity, requestCode, installReferrerString);
      }
docs: Method shows play store install prompt for the full app. Use this method only if you have custom parameters to pass to the full app using referrer else use
  {@link #showInstallPrompt(Activity, int)}
  
  @param activity    Current activity
  @param requestCode Request code for the activity to receive the result
  @param referrer    Any custom referrer string to pass to full app (must be of format "referrer_key1=referrer_value1%26referrer_key2=referrer_value2")
  @return {@code true} if install prompt is shown to user