(minor) Add TODO comment regarding the location of get_model_cache_key().

Author: RyanJDick

invokeai/backend/model_manager/load/model_cache/model_cache.py

@@ -24,6 +24,7 @@
 MB = 2**20
 
 
+# TODO(ryand): Where should this go? The ModelCache shouldn't be concerned with submodels.
 def get_model_cache_key(model_key: str, submodel_type: Optional[SubModelType] = None) -> str:
     if submodel_type:
         return f"{model_key}:{submodel_type.value}"