code: function cacheHas(cache, value) {
          var map = cache.__data__;
          if (isKeyable(value)) {
            var data = map.__data__, hash = typeof value == 'string' ? data.string : data.hash;
            return hash[value] === HASH_UNDEFINED;
          }
          return map.has(value);
        }
docs: Checks if `value` is in `cache`.
  
  @private
  @param {Object} cache The set cache to search.
  @param {*} value The value to search for.
  @returns {number} Returns `true` if `value` is found, else `false`.