step: remove step parameter from decorated functions signature

The step parameter that some functions decorated with @step take is for
internal use only and passing it as an argument when calling the wrapped
function has no effect. For the inspect tooling to report the correct
signature for the wrapped function we need to remove the parameter from
the list.

Signed-off-by: Daniel Wagenknecht <dwagenknecht@emlix.com>

Author: Daniel Wagenknecht

labgrid/step.py

@@ -227,6 +227,9 @@ def wrapper(*_args, **_kwargs):
                 step.stop()
             return _result
 
+        wrapper.__signature__ = signature.replace(
+            parameters=[p for p in signature.parameters.values() if p.name != "step"]
+        )
         return wrapper
 
     return decorator