<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def marvcli_tag(ctx, add, remove, datasets):
 """Add or remove tags to datasets"""

    if not any([add, remove]) or not datasets:
        click.echo(ctx.get_help())
        ctx.exit(1)

    app = create_app()
    setids = parse_setids(datasets)
    app.site.tag(setids, add, remove)