Add warning about not saving modal_results

To save modal_results inside CampbellResults we would need to edit the
data dictionary which is dumped in the .toml file.
The key for each modal_result would need to be changed from float to str
and we would need to add nested dicts inside data to store the modal
result.
The load method for the CampbellResults class would also need to be
modified to first load the modal_results and then the remaining data to
be able to instantiate the CampbellResults.

ross/results.py

@@ -85,6 +85,12 @@ def save(self, file):
             data = {}
 
         data[f"{self.__class__.__name__}"] = args
+
+        try:
+            del data["CampbellResults"]["modal_results"]
+        except KeyError:
+            pass
+
         with open(file, "w") as f:
             toml.dump(data, f, encoder=toml.TomlNumpyEncoder())
 
@@ -148,6 +154,8 @@ def load(cls, file):
 
         data = toml.load(file)
         data = list(data.values())[0]
+        if cls == CampbellResults:
+            data["modal_results"] = None
         for key, value in data.items():
             if key == "rotor":
                 aux_file = str(file)[:-5] + "_rotor" + str(file)[-5:]
@@ -1667,6 +1675,20 @@ def _plot_with_mode_shape_callback(trace, points, state):
 
         return VBox([camp_fig, plot_mode_3d])
 
+    def save(self, file):
+        # TODO save modal results
+        warn(
+            "The CampbellResults.save method is not saving the attribute 'modal_results' for now."
+        )
+        super().save(file)
+
+    @classmethod
+    def load(cls, file):
+        warn(
+            "The CampbellResults.save method is not saving the attribute 'modal_results' for now."
+        )
+        return super().load(file)
+
 
 class FrequencyResponseResults(Results):
     """Class used to store results and provide plots for Frequency Response.