code: function(key) {
          this._removeAddsOrRemoves(this.flags.set, key);
          if (this.flags.remove.indexOf(key) === -1) {
              this.flags.remove.push(key);
          }
          return this;
      }
docs: Remove a flag from a map.
  @method removeFlag
  @param {String} key the key for the flag in the map.
  @chainable