def instances(klass)
      files.map do |plugin_file|
        plugin_file.instances.select { |inst| inst.is_a?(klass) }
      end.flatten
    end
def instances(klass)
      files.map do |plugin_file|
        plugin_file.instances.select { |inst| inst.is_a?(klass) }
      end.flatten
    end
@param path [String]

 @param [Class] klass  base class of all instances

 @return [Array<CheckerTransformerBase>]