'_TableBaseHDU verify method.'

def _verify(self, option='warn'):

    errs = super(_TableBaseHDU, self)._verify(option=option)
    self.req_cards('NAXIS', None, (lambda v: (v == 2)), 2, option, errs)
    self.req_cards('BITPIX', None, (lambda v: (v == 8)), 8, option, errs)
    self.req_cards('TFIELDS', 7, (lambda v: (_is_int(v) and (v >= 0) and (v <= 999))), 0, option, errs)
    tfields = self._header['TFIELDS']
    for idx in range(tfields):
        self.req_cards(('TFORM' + str((idx + 1))), None, None, None, option, errs)
    return errs
