[Discuss-gnuradio] How to use gr.buffer

[Zhonghua]

Hi every one,
I want to use a buffer to receive streams from my transmitter module, 
read streams from this buffer and send the obtained streams to my 
receiver module. I followed the document of "Simple User Manual for 
Gnuradio 3.1.1" to use buffer as the format: 
buf=gr.buffer(4000,gr.sizeof_gr_complex). There is an error says 
"TypeError: Required argument 'link' (pos 3) not found". I checked some 
information and knew there should be a 'gr_block_sptr link' in the arg 
lists. But I don't know the detail of usage. I looked up from Google but 
got nothing helpful. There even has no one instance showing how to use 
buffer in gnu radio. I can only see some explains that how the buffer be 
constructed in C++ modules. Anybody used buffer in gnuradio? Thanks for 
your instruction.

BR,
Zhonghua