Fix for making student ProphetNet for Seq2Seq Distillation (#12130)

* make_student.py: fix to make student ProphetNet

* reformat

examples/research_projects/seq2seq-distillation/make_student.py

@@ -118,11 +118,17 @@ def create_student_by_copying_alternating_layers(
             d = teacher_d
         init_kwargs.update({"encoder_layers": e, "decoder_layers": d})
     except AttributeError:  # T5
+        if hasattr(teacher.config, "num_encoder_layers"):
+            teacher_e, teacher_d = teacher.config.num_encoder_layers, teacher.config.num_decoder_layers
+        else:
             teacher_e, teacher_d = teacher.config.num_layers, teacher.config.num_decoder_layers
         if e is None:
             e = teacher_e
         if d is None:
             d = teacher_d
+        if hasattr(teacher.config, "num_encoder_layers"):
+            init_kwargs.update({"num_encoder_layers": e, "num_decoder_layers": d})
+        else:
             init_kwargs.update({"num_layers": e, "num_decoder_layers": d})
 
     # Kwargs to instantiate student: teacher kwargs with updated layer numbers + **extra_config_kwargs
@@ -150,6 +156,12 @@ def create_student_by_copying_alternating_layers(
         d_layers_to_copy: List[int] = pick_layers_to_copy(d, teacher_d)
 
     try:
+        if hasattr(
+            teacher, "prophetnet"
+        ):  # For ProphetNet, student.model.encoder.layers is called student.prophetnet.encoder.layers
+            copy_layers(teacher.prophetnet.encoder.layers, student.prophetnet.encoder.layers, e_layers_to_copy)
+            copy_layers(teacher.prophetnet.decoder.layers, student.prophetnet.decoder.layers, d_layers_to_copy)
+        else:
             copy_layers(teacher.model.encoder.layers, student.model.encoder.layers, e_layers_to_copy)
             copy_layers(teacher.model.decoder.layers, student.model.decoder.layers, d_layers_to_copy)
     except AttributeError:  # For t5, student.model.encoder.layers is called student.encoder.block