public boolean contains(Object o) {
            return containsValue(o);
        }
Returns a {@link Collection} view of the values contained in this map.
The collection is backed by the map, so changes to the map are reflected
in the collection, and vice-versa. If the map is modified while an
iteration over the collection is in progress (except through the
iterator's own <tt>remove</tt> operation), the results of the iteration
are undefined. The collection supports element removal, which removes the
corresponding mapping from the map, via the <tt>Iterator.remove</tt>,
<tt>Collection.remove</tt>, <tt>removeAll</tt>, <tt>retainAll</tt> and
<tt>clear</tt> operations. It does not support the <tt>add</tt> or
<tt>addAll</tt> operations.
src/main/java/com/alibaba/fastjson/util/AntiCollisionHashMap.java