Add comment about "traced" naming convention (#1037)

sockeye/model.py

@@ -322,8 +322,13 @@ def save_parameters(self, fname: str):
         :param fname: Path to save parameters to.
         """
         self.apply(layers.interleave_kv)
-        # Do not save parameters for traced modules. Traced modules are created
-        # at runtime and use the same parameters as non-traced versions.
+        # Sockeye follows the convention of using the "traced" prefix for
+        # modules that are created at runtime by tracing other modules.
+        # Ex: traced_encoder = trace(encoder, ...)
+        # Traced modules use the same parameters as the original versions so we
+        # filter their names from the state dictionary to avoid saving redundant
+        # copies of their parameters. Copies can also cause errors at loadtime
+        # if the traced modules do not yet exist.
         filtered_state_dict = {name: param for (name, param) in self.state_dict().items() if 'traced' not in name}
         pt.save(filtered_state_dict, fname)
         self.apply(layers.separate_kv)