def to_yaml
      require 'yaml'
      trackers_export = @trackers.reduce({}) do |export, tracker|
        export[tracker.title] = tracker.to_yaml_object; export
      end
      YAML.dump(trackers_export)
    end
def to_yaml
      require 'yaml'
      trackers_export = @trackers.reduce({}) do |export, tracker|
        export[tracker.title] = tracker.to_yaml_object; export
      end
      YAML.dump(trackers_export)
    end
Exports all the tracker results to YAML. It will call the to_yaml_object method
 for every tracker and combines these into a single YAML export.