def blockvisit(self, nodes, frame):
        """Visit a list of nodes as block in a frame.  If the current frame
        is no buffer a dummy ``if 0: yield None`` is written automatically
        unless the force_generator parameter is set to False.
        """
        if frame.buffer is None:
            self.writeline('if 0: yield None')
        else:
            self.writeline('pass')
        try:
            for node in nodes:
                self.visit(node, frame)
        except CompilerExit:
            pass
Visit a list of nodes as block in a frame.  If the current frame
        is no buffer a dummy ``if 0: yield None`` is written automatically
        unless the force_generator parameter is set to False.