/guava/guava/src/com/google/common/collect/AbstractMapBasedMultimap.java
this.ancestorDelegate = ( ancestor.getDelegate( ) ;
this.ancestorDelegate = ( ancestor == null ) ? null : ancestor.getDelegate ( ) ;
@ParametricNullness K key, Collection<V> delegate, @CheckForNull WrappedCollection ancestor) { this.key = key; this.delegate = delegate; this.ancestor = ancestor; <extra_id_0> } void refreshIfEmpty() { if (ancestor != null) { ancestor.refreshIfEmpty(); if (ancestor.getDelegate() != ancestorDelegate) { throw new ConcurrentModificationException();