'Put parentheses around self.
Returns string, baseline arguments for stringPict.
left or right can be None or empty string which means \'no paren from
that side\''

def parens(self, left='(', right=')', ifascii_nougly=False):

    h = self.height()
    b = self.baseline
    if (ifascii_nougly and (not pretty_use_unicode())):
        h = 1
        b = 0
    res = self
    if left:
        lparen = stringPict(vobj(left, h), baseline=b)
        res = stringPict(*lparen.right(self))
    if right:
        rparen = stringPict(vobj(right, h), baseline=b)
        res = stringPict(*res.right(rparen))
    return ('\n'.join(res.picture), res.baseline)
