fix pipeline compatibility with diffusers>=0.29

pipeline.py

@@ -8,7 +8,10 @@ from diffusers import UNet2DConditionModel
 from diffusers.configuration_utils import register_to_config
 from diffusers.models.attention import BasicTransformerBlock
 from diffusers.models.resnet import ResnetBlock2D, Downsample2D, Upsample2D
-from diffusers.models.transformer_2d import Transformer2DModelOutput
+try:
+    from diffusers.models.transformer_2d import Transformer2DModelOutput
+except ImportError:
+    from diffusers.models.transformers.transformer_2d import Transformer2DModelOutput
 from diffusers.pipelines.stable_diffusion import StableDiffusionSafetyChecker
 from diffusers.schedulers import KarrasDiffusionSchedulers
 from torch import nn