/guava/guava/src/com/google/common/collect/Synchronized.java
if ( ( asMap) == null) {   asMap = new SynchronizedAsMap( delegate( ).asMap( ) , mutex) ; }
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return asMap; } } @Override public Multiset<K> keys() { synchronized (mutex) { <extra_id_0> keys = multiset(delegate().keys(), mutex); } return keys; } } @Override