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packages/collection/lib/equality.dart

 // Copyright (c) 2013, 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.
 
 /**
  * Defines equality relations on collections.
  */
 library dart.pkg.collection.equality;
 
 import "dart:collection";
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       if (o is List) return new ListEquality(this).hash(o);
       if (o is Iterable) return new IterableEquality(this).hash(o);
     } else if (o is Iterable) {
       return new UnorderedIterableEquality(this).hash(o);
     }
     return _base.hash(o);
   }
 
   bool isValidKey(Object o) => o is Iterable || o is Map || _base.isValidKey(o);
 }