Add FlaxModelMixin to __init__.py

Author: mishig25

src/diffusers/__init__.py

@@ -10,6 +10,7 @@
 __version__ = "0.4.0.dev0"
 
 from .configuration_utils import ConfigMixin
+from .modeling_flax_utils import FlaxModelMixin
 from .modeling_utils import ModelMixin
 from .models import AutoencoderKL, UNet2DConditionModel, UNet2DModel, VQModel
 from .onnx_utils import OnnxRuntimeModel