diagram filter error

Hi again,

using madgraph 2.9.2 I tried to use a diagram filter (to sort diagrams in a
complicated background) and I had the same problem as reported in
https://answers.launchpad.net/mg5amcnlo/+question/695863

I applied the patch you pointed to as
patch misc.py 304_303.diff
so that the error message about the level is now gone.

But it is now producing a different error:
"TypeError : remove_diag() takes 1 positional argument but 2 were given"

The filter I'm using is trivial, just to reproduce the problem:
def remove_diag(diag):
    return False
It works just fine with version 2.6. Has the syntax changed in 2.9?

Any help would be gratefully appreciated.