code: function (str, opts) {
      opts = extend({marker: 'snippet', action: 'add'}, opts);
      opts = extend({}, this.options, opts);
  
      var snippet = this.toSnippet(str, opts);
      return utils.inject(this, snippet, opts);
    }
docs: Inject the snippet's contents into the given `string` at the
  defined point of insertion (`<!-- snippet -->`)
  
  @name .inject
  @param  {String} `str`
  @param  {Object} `opts`
  @api public