pkg: analysis aided cleanup

pkg/yaml/lib/src/model.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 /// This file contains the node classes for the internal representations of YAML
 /// documents. These nodes are used for both the serialization tree and the
 /// representation graph.
 library model;
 
-import 'model.dart';
 import 'parser.dart';
 import 'utils.dart';
 import 'visitor.dart';
 import 'yaml_exception.dart';
 
 /// A tag that indicates the type of a YAML node.
 class Tag {
   // TODO(nweiz): it would better match the semantics of the spec if there were
   // a singleton instance of this class for each tag.
 
@@ skipping 207 matching lines @@
     var strContent = content.keys
         .map((k) => '${k}: ${content[k]}')
         .join(', ');
     return '$tag {$strContent}';
   }
 
   int get hashCode => super.hashCode ^ hashCodeFor(content);
 
   visit(Visitor v) => v.visitMapping(this);
 }