by `using` you can get tidy lines, for example:

    using picojson::value;
    reply["volume_controls"] = value(MapToJSArray<VolumeControl*>(volume_controls_));
    reply["mute_controls"] = value(MapToJSArray<MuteControl*>(mute_controls_));
    reply["devices"] = value(MapToJSArray<AudioDevice*>(audio_devices_));
    reply["streams"] = value(MapToJSArray<AudioStream*>(audio_streams_));
    reply["audio_groups"] = value(MapToJSArray<AudioGroup*>(audio_groups_));