'Matches any extension HDU that is not one of the standard extension HDU
types.'

@classmethod
def match_header(cls, header):

    card = header.cards[0]
    xtension = card.value
    if isinstance(xtension, string_types):
        xtension = xtension.rstrip()
    standard_xtensions = ('IMAGE', 'TABLE', 'BINTABLE', 'A3DTABLE')
    return ((card.keyword == 'XTENSION') and (xtension not in standard_xtensions))
