AttributeError: 'DataParallel' object has no attribute 'backbone'

This error occurs when you try to access an attribute that doesn't exist in the object of the class DataParallel.

The DataParallel class is used in PyTorch to parallelize the training process across multiple GPUs. It creates multiple replicas of the model on each GPU and distributes the data to each replica for processing.

To resolve the error, you need to make sure that you are calling the correct attribute of the model. In this case, the 'backbone' attribute is not available in the DataParallel object.

You can access the model by calling the .module attribute of the DataParallel object. For example:

model = DataParallel(model)
...
model.module.backbone

This will give you access to the 'backbone' attribute of the model.