add nave to save/load roundtrip

mne/time_frequency/spectrogram.py

@@ -186,6 +186,8 @@ def __getstate__(self):
             data_type=self._data_type,
             info=self.info,
         )
+        if hasattr(self, "nave"):
+            out.update(nave=self.nave)
         return out
 
     def __setstate__(self, state):
@@ -202,6 +204,8 @@ def __setstate__(self, state):
         self.info = Info(**state["info"])
         self._data_type = state["data_type"]
         self.preload = True
+        if "nave" in state:
+            self._nave = state["nave"]
         # instance type
         inst_types = dict(Raw=Raw, Epochs=Epochs, Evoked=Evoked)
         self._inst_type = inst_types[state["inst_type_str"]]
@@ -1222,6 +1226,7 @@ def __init__(
             **method_kw,
         )
 
+        # TODO are there other properties of `inst` we should propagate here?
         self._nave = inst.nave
 
     @property