Returns an embed field value based on the parameters.

def process_embed(embed_items=None,
                  embed_tracks=None,
                  embed_metadata=None,
                  embed_insights=None):
    """Returns an embed field value based on the parameters."""

    result = None

    embed = ''
    if embed_items:
        embed = 'items'
    if embed_tracks:
        if embed != '':
            embed += ','
        embed += 'tracks'
    if embed_metadata:
        if embed != '':
            embed += ','
        embed += 'metadata'
    if embed_insights:
        if embed != '':
            embed += ','
        embed += 'insights'

    if embed != '':
        result = embed

    return result