Check that qualifiers are expected values.

def _chk_qualifier(self, qualifiers, flds, lnum):
        """Check that qualifiers are expected values."""
        # http://geneontology.org/page/go-annotation-conventions#qual
        for qual in qualifiers:
            if qual not in AnnoReaderBase.exp_qualifiers:
                errname = 'UNEXPECTED QUALIFIER({QUAL})'.format(QUAL=qual)
                self.illegal_lines[errname].append((lnum, "\t".join(flds)))