Join the parts of a URI back together to form a valid URI.

        pieces is a tuble of URI pieces.  The scheme must be in pieces[0] so that
        the rest of the pieces can be interpreted.

def unparse(self, pieces, defaults=None):
        """Join the parts of a URI back together to form a valid URI.

        pieces is a tuble of URI pieces.  The scheme must be in pieces[0] so that
        the rest of the pieces can be interpreted.

        """
        return self.parser_for(pieces[0])(defaults).unparse(pieces)