'Matches any HDU that has the \'SIMPLE\' keyword but is not a standard
Primary or Groups HDU.'

@classmethod
def match_header(cls, header):

    card = header.cards[0]
    if (card.keyword == 'SIMPLE'):
        if (('GROUPS' not in header) and (card.value is False)):
            return True
        else:
            raise InvalidHDUException
    else:
        return False
