Resolve "release v1.2.0"

Closes #257 (closed)

mlair/plotting/tracker_plot.py

@@ -119,11 +119,13 @@ class TrackChain:
                 control_obj = control[variable][scope]
                 if method == "set":
                     track_objects = self._add_set_object(track_objects, tr, control_obj)
-                elif method == "get":
+                elif method == "get":  # pragma: no branch
                     track_objects, skip_control_update = self._add_get_object(track_objects, tr, control_obj,
                                                                               control, scope, variable)
                     if skip_control_update is True:
                         continue
+                else:  # pragma: no cover
+                    raise ValueError(f"method must be either set or get but given was {method}.")
                 self._update_control(control, variable, scope, tr)
         return track_objects, control