anchor.diff:  @anonymous
   class GtagEvent {
     external factory GtagEvent({
  -    String event_category,
  -    String event_label, // Event e.g., gaScreenViewEvent, gaSelectEvent, etc.
  -    String send_to, // UA ID of target GA property to receive event data.
  +    String? event_category,
  +    String? event_label, // Event e.g., gaScreenViewEvent, gaSelectEvent, etc.
  +    String? send_to, // UA ID of target GA property to receive event data.
   
  -    int value,
  -    bool non_interaction,
  +    int value = 0,
  +    bool non_interaction = false,
       dynamic custom_map,
     });
   
  
positive.code: // Use of this source code is governed by a BSD-style license that can be
  // found in the LICENSE file.
  
  // @dart=2.9
  
  @JS()
  library gtags;
  
negative.code: @anonymous
  class GtagException {
    external factory GtagException({
      String? description,
      bool fatal = false,
    });
  
    external String get description; // Description of the error.
  