Sphinx documentation of class methods is incomplete

see e.g. export.VTKExporter, https://yade-dem.org/doc/yade.export.html#yade.export.VTKExporter . The documentation of exportSpheres and exportFacets function does not looks good and does not have documented parameters (although same docstring produced good documentation for functions in the same module)

Original bug report by Jan Stránský on 2012-07-31 : https://bugs.launchpad.net/yade/+bug/1031215

The same problem appears apparently for all nested doc (i.e. documented function in a python class) Like here: https://yade-dem.org/doc/yade.post2d.html?highlight=helixflatten#yade.post2d.HelixFlatten

I don't see any mistake in the formatting of the docstring itself so I guess the solution is at a diferent level (conf.py, typically). No clue how to fix presently.

Original bug report by Bruno Chareyre on 2013-03-06 : https://bugs.launchpad.net/yade/+bug/1031215