anchor.diff:    @override
     Map toJson() {
       return (buildJson
  -      ..add('sdk', sdkConstraint)
  +      ..add('sdk', "'${sdkConstraint.toString()}'")
         ..addAll(unParsedYaml)).json;
     }
   }
  
positive.code:       ..add('version', version)
        ..add('homepage', homepage)
        ..add('documentation', documentation)
        ..add('description', description)
        ..add('dependencies', dependencies)
        ..add('dev_dependencies', devDependencies)
  
negative.code:             ? documentation
              : this.documentation,
          description: description != null ? description : this.description,
          environment: environment != null ? environment : this.environment,
          dependencies: dependencies != null ? dependencies : this.dependencies,
          devDependencies: devDependencies != null
              ? devDependencies
  