def parse_itypes(itype_argument):
    """Parses the itype argument and returns a set of strings with all the selected interaction types """
    if "all" in itype_argument:
        return ["sb", "pc", "ps", "ts", "vdw", "hb", "lhb", "hbbb", "hbsb",
                "hbss", "wb", "wb2", "hls", "hlb", "lwb", "lwb2"]
    return set(itype_argument.split(","))