def _make_expr(self):
    ctype = self.table._get_type(self.name)
    klass = ctype.column_type()
    return klass(self, name=self.name)
def _make_expr(self):
    ctype = self.table._get_type(self.name)
    klass = ctype.column_type()
    return klass(self, name=self.name)