code: function mapCacheSet(key, value) {
      var data = getMapData(this, key),
        size = data.size;
  
      data.set(key, value);
      this.size += data.size == size ? 0 : 1;
      return this;
    }
docs: Sets the map `key` to `value`.
  
  @private
  @name set
  @memberOf MapCache
  @param {string} key The key of the value to set.
  @param {*} value The value to set.
  @returns {Object} Returns the map cache instance.