Return a unicode object with the MATCH representation of this UnaryTransformation.

def to_match(self):
        """Return a unicode object with the MATCH representation of this UnaryTransformation."""
        self.validate()

        translation_table = {
            u'size': u'size()',
        }
        match_operator = translation_table.get(self.operator)
        if not match_operator:
            raise AssertionError(u'Unrecognized operator used: '
                                 u'{} {}'.format(self.operator, self))

        template = u'%(inner)s.%(operator)s'
        args = {
            'inner': self.inner_expression.to_match(),
            'operator': match_operator,
        }
        return template % args