Return user-specified keyword args in a dictionary and a set (for True/False items).

def get_kwargs_set(args, exp_elem2dflt):
    """Return user-specified keyword args in a dictionary and a set (for True/False items)."""
    arg_set = set()  # For arguments that are True or False (present in set if True)
    # Add user items if True
    for key, val in args.items():
        if exp_elem2dflt is not None and key in exp_elem2dflt and val:
            arg_set.add(key)
    # Add defaults if needed
    for key, dfltval in exp_elem2dflt.items():
        if dfltval and key not in arg_set:
            arg_set.add(key)
    return arg_set