function contains(obj, val) {
  return containsValue(obj, val);
}
Whether the object/hash/map contains the given object as a value.
An alias for containsValue(obj, val).
@param {?Object<K,V>} obj The object in which to look for val.
@param {V} val The object for which to check.
@return {boolean} true if val is present.
@template K,V