public boolean containsKey(K key) {
        final Map<K, V> map = ref != null ? ref.get() : null;
        return map != null && map.containsKey(key);
    }
Produces the cache values collection.
@return the cache values collection
standalone-metastore/metastore-common/src/main/java/org/apache/hadoop/hive/metastore/properties/SoftCache.java