SwigPtrView: look up unhandled attributes in _swigptr

So far, only the explicitly listed attributes are accessible directly via SwigPtrView.
Things like ReturnData.ny are only available through ReturnDataView.ptr.ny, which is inconvenient.
Let's just look all non-private attributes that are not already explicitly handled by SwigPtrView
on _swigptr and return them as is.

python/sdist/amici/numpy.py

@@ -55,15 +55,18 @@ def __getitem__(self, item: str) -> Union[np.ndarray, float]:
         if item in self._cache:
             return self._cache[item]
 
-        if item == "id":
-            return getattr(self._swigptr, item)
+        if item in self._field_names:
+            value = _field_as_numpy(
+                self._field_dimensions, item, self._swigptr
+            )
+            self._cache[item] = value
 
-        if item not in self._field_names:
-            self.__missing__(item)
+            return value
+
+        if not item.startswith("_") and hasattr(self._swigptr, item):
+            return getattr(self._swigptr, item)
 
-        value = _field_as_numpy(self._field_dimensions, item, self._swigptr)
-        self._cache[item] = value
-        return value
+        self.__missing__(item)
 
     def __missing__(self, key: str) -> None:
         """

python/sdist/amici/plotting.py

@@ -109,7 +109,7 @@ def plot_observable_trajectories(
     if not ax:
         fig, ax = plt.subplots()
     if not observable_indices:
-        observable_indices = range(rdata["y"].shape[1])
+        observable_indices = range(rdata.ny)
 
     if marker is None:
         # Show marker if only one time point is available,

python/tests/test_swig_interface.py

@@ -511,6 +511,9 @@ def test_rdataview(sbml_example_presimulation_module):
     rdata = amici.runAmiciSimulation(model, model.getSolver())
     assert isinstance(rdata, amici.ReturnDataView)
 
+    # check that non-array attributes are looked up in the wrapped object
+    assert rdata.ptr.ny == rdata.ny
+
     # fields are accessible via dot notation and [] operator,
     #  __contains__ and __getattr__ are implemented correctly
     with pytest.raises(AttributeError):