Fix setting Model.module

Ensure `Model.module` gets set during `Model.clone()`.
So far, this was only set during `model_module.get_model`.
Fixes unpickling of cloned Models.

Also implement `ModelPtr.__reduce__` in addition to `Model.__reduce__` (#2985).

Author: dweindl

CHANGELOG.md

@@ -64,13 +64,13 @@ See also our [versioning policy](https://amici.readthedocs.io/en/latest/versioni
   This is a wrapper for both `amici.run_simulation` and
   `amici.run_simulations`, depending on the type of the `edata` argument.
   It also supports passing some `Solver` options as keyword arguments.
-* Improved `pickle` support for `amici.{ModelPtr,Solver,ExpData`.
+* Improved `pickle` support for `amici.{Model,ModelPtr,Solver,ExpData`.
   Note that AMICI's pickling support is only intended for short-term storage
   or inter-process communication.
   Reading pickled objects after updating AMICI or the model code will almost
   certainly fail.
-  * `amici.ModelPtr` now supports sufficient pickling for use in
-    multi-processing contexts. This works only if the amici-generated model
+  * `amici.Model`and `amici.ModelPtr` now support sufficient pickling for use
+    in multi-processing contexts. This works only if the amici-generated model
     package exists in the same file system location and does not change until
     unpickling.
   * `amici.Solver` is now picklable if amici was built with HDF5 support.

python/tests/test_swig_interface.py

@@ -698,6 +698,10 @@ def test_pickle_model(sbml_example_presimulation_module):
         != model_pickled.get_steady_state_sensitivity_mode()
     )
 
+    # ensure we can pickle after clone()
+    model_clone = model.clone()
+    pickle.loads(pickle.dumps(model_clone))
+
 
 def test_pickle_edata():
     ny = 2

swig/model.i

@@ -108,12 +108,38 @@ using namespace amici;
 %newobject amici::Model::clone;
 
 %rename(create_solver) amici::Model::get_solver;
+%rename(_cpp_model_clone) amici::Model::clone;
 
 %extend amici::Model {
 %pythoncode %{
+def clone(self):
+    """Clone the model instance."""
+    clone = self._cpp_model_clone()
+    try:
+        # copy module reference if present
+        clone.module = self.module
+    except Exception:
+        pass
+
+    return clone
+
 def __deepcopy__(self, memo):
     return self.clone()
 
+def __reduce__(self):
+    from amici.swig_wrappers import restore_model, get_model_settings, file_checksum
+
+    return (
+        restore_model,
+        (
+            self.get_name(),
+            Path(self.module.__spec__.origin).parent,
+            get_model_settings(self),
+            file_checksum(self.module.extension_path),
+        ),
+        {}
+    )
+
 @overload
 def simulate(
     self: AmiciModel,
@@ -192,6 +218,17 @@ def simulate(
 
 %extend std::unique_ptr<amici::Model> {
 %pythoncode %{
+def clone(self):
+    """Clone the model instance."""
+    clone = self._cpp_model_clone()
+    try:
+        # copy module reference if present
+        clone.module = self.module
+    except Exception:
+        pass
+
+    return clone
+
 def __deepcopy__(self, memo):
     return self.clone()