Return the set of GUIDs found in guid_string

    :param str guid_string:
        String containing zero or more GUIDs.  Each GUID may or may not be
        enclosed in {}

    Example data (this string contains two distinct GUIDs):

    PARENT_SNAPSHOT_ID                      SNAPSHOT_ID
                                            {a5b8999f-5d95-4aff-82de-e515b0101b66}
    {a5b8999f-5d95-4aff-82de-e515b0101b66} *{a7345be5-ab66-478c-946e-a6c2caf14909}

def _find_guids(guid_string):
    '''
    Return the set of GUIDs found in guid_string

    :param str guid_string:
        String containing zero or more GUIDs.  Each GUID may or may not be
        enclosed in {}

    Example data (this string contains two distinct GUIDs):

    PARENT_SNAPSHOT_ID                      SNAPSHOT_ID
                                            {a5b8999f-5d95-4aff-82de-e515b0101b66}
    {a5b8999f-5d95-4aff-82de-e515b0101b66} *{a7345be5-ab66-478c-946e-a6c2caf14909}
    '''
    guids = []
    for found_guid in re.finditer(GUID_REGEX, guid_string):
        if found_guid.groups():
            guids.append(found_guid.group(0).strip('{}'))
    return sorted(list(set(guids)))