code: protected final Reference<K, V> getReference(Object key, Restructure restructure) {
  		int hash = getHash(key);
  		return getSegmentForHash(hash).getReference(key, hash, restructure);
  	}
docs: Return a {@link Reference} to the {@link Entry} for the specified {@code key},
  or {@code null} if not found.
  @param key the key (can be {@code null})
  @param restructure types of restructure allowed during this call
  @return the reference, or {@code null} if not found