'this' parameter keyword unsupported

[vadi2]

The following sphinx code:

.. method:: IApplicationBuilder UseVonkInteraction<TService>(this IApplicationBuilder app, Expression<Action<<TService, IVonkContext>> handler, OperationType operationType = OperationType.Handler)

Doesn't work, unfortunately:

Exception occurred:
  File "/home/vadi/.local/lib/python2.7/site-packages/sphinx_csharp/csharp.py", line 114, in parse_param_signature
    raise RuntimeError('Parameter signature invalid, got ' + sig)
RuntimeError: Parameter signature invalid, got this IApplicationBuilder app