anchor.diff:    }
   
     Future<void> _handlePullRequest(String rawRequest) async {
  -    // ignore: undefined_class
       final PullRequestEvent pullRequestEvent =
           await _getPullRequestEvent(rawRequest);
       if (pullRequestEvent == null) {
         throw const BadRequestException('Expected pull request event.');
       }
  -    // ignore: invalid_assignment
       final String eventAction = pullRequestEvent.action;
  -    // ignore: invalid_assignment
       final PullRequest pr = pullRequestEvent.pullRequest;
   
       // See the API reference:
  
positive.code: 
  import 'package:crypto/crypto.dart';
  import 'package:github/github.dart';
  import 'package:meta/meta.dart';
  import 'package:github/hooks.dart';
  
  import '../datastore/cocoon_config.dart';
  import '../model/appengine/service_account_info.dart';
  
negative.code:     return bodySignature == signature;
    }
  
    Future<PullRequestEvent> _getPullRequestEvent(String request) async {
      if (request == null) {
        return null;
      }
      try {
        return PullRequestEvent.fromJson(
            json.decode(request) as Map<String, dynamic>);
      } on FormatException {
  