add some comments

src/diffusers/pipeline_utils.py

@@ -114,6 +114,7 @@ class DiffusionPipeline(ConfigMixin):
         local_files_only = kwargs.pop("local_files_only", False)
         use_auth_token = kwargs.pop("use_auth_token", None)
         
+        # 1. Download the checkpoints and configs
         # use snapshot download here to get it working from from_pretrained
         if not os.path.isdir(pretrained_model_name_or_path):
             cached_folder = snapshot_download(
@@ -129,11 +130,12 @@ class DiffusionPipeline(ConfigMixin):
 
         config_dict = cls.get_config_dict(cached_folder)
 
-        module = config_dict["_module"]
+        # 2. Get class name and module candidates to load custom models
         class_name_ = config_dict["_class_name"]
         module_candidate = config_dict["_module"]
         module_candidate_name = module_candidate.replace(".py", "")
 
+        # 3. Load the pipeline class, if using custom module then load it from the hub
         # if we load from explicit class, let's use it
         if cls != DiffusionPipeline:
             pipeline_class = cls
@@ -147,6 +149,7 @@ class DiffusionPipeline(ConfigMixin):
 
         init_kwargs = {}
 
+        # 4. Load each module in the pipeline
         for name, (library_name, class_name) in init_dict.items():
             # if the model is not in diffusers or transformers, we need to load it from the hub
             # assumes that it's a subclass of ModelMixin
@@ -156,6 +159,7 @@ class DiffusionPipeline(ConfigMixin):
                 importable_classes = ALL_IMPORTABLE_CLASSES
                 class_candidates = {c: class_obj for c in ALL_IMPORTABLE_CLASSES.keys()}
             else:
+                # else we just import it from the library.
                 library = importlib.import_module(library_name)
                 class_obj = getattr(library, class_name)
                 importable_classes = LOADABLE_CLASSES[library_name]
@@ -168,12 +172,15 @@ class DiffusionPipeline(ConfigMixin):
 
             load_method = getattr(class_obj, load_method_name)
 
+            # check if the module is in a subdirectory
             if os.path.isdir(os.path.join(cached_folder, name)):
                 loaded_sub_model = load_method(os.path.join(cached_folder, name))
             else:
+                # else load from the root directory
                 loaded_sub_model = load_method(cached_folder)
 
             init_kwargs[name] = loaded_sub_model  # UNet(...), # DiffusionSchedule(...)
 
+        # 5. Instantiate the pipeline
         model = pipeline_class(**init_kwargs)
         return model