def sponsor_sort(sort):
    """
    Returns the actual name of the key to sort by.
    """
    if sort == 'id':
        return '_id'
    elif sort == 'sponsor':
        return 'account'
    elif sort == 'witness':
        return 'is_witness'
    elif sort == 'percentage':
        return 'percentage_total_vesting_shares'
    else:
        return 'vesting_shares'
