code: function(css) {
      this.loadThemeData();
      return css.replace(this.fieldRegexAll, function(match, fieldName) {
        return this.vars[fieldName] || fieldName;
      }.bind(this));
    }
docs: Replaces parsed field identifiers into mapped variable values.
  Example: "____color-primary____" >> "#f00"
  This method is intended to run on rendered CSS containing parsed fields.
  @param {String} css string to find and replace parsed fields within.
  @returns {String} the rendered string with fields formatted as values.