some fixes and improvements

python_app/workflows/sequential_capture_workflow.py

@@ -179,8 +179,8 @@ class SequentialCaptureSession:
             self._next_index = len(self._combos)
             return combined_collection.traces[-1]
 
-        assert self._input_switch is not None
-        assert self._output_switch is not None
+        if self._input_switch is None or self._output_switch is None:
+            raise RuntimeError("Switches are not initialised for combo capture")
         self._output_switch.switch_to(combo.output)
         self._input_switch.switch_to(combo.input)
         if self._config.runtime.settling_ms > 0: