Split line into field values.

def _split_line(self, line):
        """Split line into field values."""
        line = line.rstrip('\r\n')
        flds = re.split('\t', line)
        assert len(flds) == self.exp_numcol, "EXPECTED({E}) COLUMNS, ACTUAL({A}): {L}".format(
            E=self.exp_numcol, A=len(flds), L=line)
        return flds