code: function(k, dflt, defaultKey) {
        if (defaultKey) {
          return this.has(k) ? this.values[k] : dflt[defaultKey];
        }
        return this.has(k) ? this.values[k] : dflt;
      }
docs: Return the value for a key, or a default value. If 'defaultKey' is passed then 'dflt' is assumed to be an object with a number of possible default values as properties where 'defaultKey' is the key of the property that will be chosen; otherwise it's assumed to be a single value.