Q:

What does 'cb' in cb_kwargs stand for?

What does cb in cb_kwargs (one entry in parameter list of python) stand for?
I believe kwargs means keyword arguments. But I don’t have no idea about cb.

A:

Callback, I believe. Not necessary though.

A:

cb_kwargs is not a python reserved keyword or builtin function, so it can mean anything depending on context.
However, I believe that the typical use is as a dictionary of keyword, value pairs that is meant to be passed to a callback function at some time, for example:
cb_kwargs = {'timeout':22, 'verbose':False}

Then some function callback might later be called as 
callback(**cb_kwargs)

which for this particular dictionary would be equivalent to calling it as:
callback(timeout=22, verbose=False)

