Wire LearnedFeatureImputation and map_heterogeneous_to_full for MultiTaskGP (#3296)

Summary:

X-link: facebook/Ax#5192

Automatically configures learned feature imputation for models that pad heterogeneous per-task data to the full joint feature space. Models with native heterogeneity support are excluded from this automatic configuration.

Differential Revision: D101841497

Author: Carl Hvarfner

botorch/models/heterogeneous_mtgp.py

@@ -327,6 +327,7 @@ def construct_inputs(
         rank: int | None = None,
         use_saas_prior: bool = True,
         use_combinatorial_kernel: bool = True,
+        map_heterogeneous_to_full: bool = False,
     ) -> dict[str, Any]:
         r"""Construct ``Model`` keyword arguments from a given ``MultiTaskDataset``.
 
@@ -341,6 +342,10 @@ def construct_inputs(
                 ``MultiTaskConditionalKernel``.
             use_combinatorial_kernel: Whether to use a combinatorial kernel over the
                 binary embedding of task features in ``MultiTaskConditionalKernel``.
+            map_heterogeneous_to_full: Accepted for compatibility with
+                ``MultiTaskGP.construct_inputs`` but unused.
+                ``HeterogeneousMTGP`` handles heterogeneous features via
+                ``MultiTaskConditionalKernel``.
         """
         if training_data.task_feature_index != -1:
             raise NotImplementedError(

test/models/test_heterogeneous_mtgp.py

@@ -97,6 +97,12 @@ def test_input_constructor(self) -> None:
         self.assertEqual(model_inputs["full_feature_dim"], 5)
         self.assertIsNone(model_inputs["rank"])
 
+        with self.subTest("map_heterogeneous_to_full accepted and ignored"):
+            model_inputs = HeterogeneousMTGP.construct_inputs(
+                training_data=self.mtds, map_heterogeneous_to_full=True
+            )
+            self.assertNotIn("map_heterogeneous_to_full", model_inputs)
+
     def test_standard_heterogeneous_mtgp(self) -> None:
         # Construct the model (inferred noise: train_Yvars is None).
         model_inputs = HeterogeneousMTGP.construct_inputs(training_data=self.mtds)