'Create a dictionary for video player configuration according to `player_mode`
:param player_mode (str): Video player mode
:param additional_data (dict): Optional additional metadata.
:return: dict'

def metadata_for_mode(self, player_mode, additional_data=None):

    metadata = {}
    youtube_ids = {'youtube_id_1_0': '', 'youtube_id_0_75': '', 'youtube_id_1_25': '', 'youtube_id_1_5': ''}
    if (player_mode == 'html5'):
        metadata.update(youtube_ids)
        metadata.update({'html5_sources': HTML5_SOURCES})
    if (player_mode == 'youtube_html5'):
        metadata.update({'html5_sources': HTML5_SOURCES})
    if (player_mode == 'youtube_html5_unsupported_video'):
        metadata.update({'html5_sources': HTML5_SOURCES_INCORRECT})
    if (player_mode == 'html5_unsupported_video'):
        metadata.update(youtube_ids)
        metadata.update({'html5_sources': HTML5_SOURCES_INCORRECT})
    if (player_mode == 'hls'):
        metadata.update(youtube_ids)
        metadata.update({'html5_sources': HLS_SOURCES})
    if (player_mode == 'html5_and_hls'):
        metadata.update(youtube_ids)
        metadata.update({'html5_sources': (HTML5_SOURCES + HLS_SOURCES)})
    if additional_data:
        metadata.update(additional_data)
    return metadata
