code: function(attrs, options) {
      if (typeof attrs === 'object') {
        for(var k in attrs) {
          this.set(k, attrs[k], options);
        }
      } else {
        var value = options, name = attrs;
        options = arguments[2];
        if (this[name] && this[name] === value) return this;
        this._previous[name] = this[name];
        this[name] = value;
        this.trigger('change');
      }
      return this;
    }
docs: Setter
  
  @param {object} hash of attributes
  @param {object} options
  or
  @param {string} name of attribute
  @param {string} attribute value
  @param {object} options
  @return {this}