def postinit(self, expr=None, globals=None, locals=None):
self.expr = expr<EOL>self.globals = globals<EOL>self.locals = locals<EOL>
Do some setup after initialisation.

        :param expr: The expression to be executed.
        :type expr: NodeNG or None

        :param globals:The globals dictionary to execute with.
        :type globals: NodeNG or None

        :param locals: The locals dictionary to execute with.
        :type locals: NodeNG or None