[Modular] Add experimental feature warning for Modular Diffusers (#12127)

update

src/diffusers/modular_pipelines/__init__.py

@@ -7,9 +7,15 @@ from ..utils import (
     get_objects_from_module,
     is_torch_available,
     is_transformers_available,
+    logging,
 )
 
 
+logger = logging.get_logger(__name__)
+logger.warning(
+    "Modular Diffusers is currently an experimental feature under active development. The API is subject to breaking changes in future releases."
+)
+
 # These modules contain pipelines from multiple libraries/frameworks
 _dummy_objects = {}
 _import_structure = {}
@@ -61,17 +67,8 @@ if TYPE_CHECKING or DIFFUSERS_SLOW_IMPORT:
             PipelineState,
             SequentialPipelineBlocks,
         )
-        from .modular_pipeline_utils import (
-            ComponentSpec,
-            ConfigSpec,
-            InputParam,
-            InsertableDict,
-            OutputParam,
-        )
-        from .stable_diffusion_xl import (
-            StableDiffusionXLAutoBlocks,
-            StableDiffusionXLModularPipeline,
-        )
+        from .modular_pipeline_utils import ComponentSpec, ConfigSpec, InputParam, InsertableDict, OutputParam
+        from .stable_diffusion_xl import StableDiffusionXLAutoBlocks, StableDiffusionXLModularPipeline
         from .wan import WanAutoBlocks, WanModularPipeline
 else:
     import sys