docs: function interpolate(phrase, options) {
      for (var arg in options) {
        if (arg !== '_' && options.hasOwnProperty(arg)) {
          // We create a new `RegExp` each time instead of using a more-efficient
          // string replace so that the same argument can be replaced multiple times
          // in the same phrase.
          phrase = phrase.replace(new RegExp('%\\{'+arg+'\\}', 'g'), options[arg]);
        }
      }
      return phrase;
    }