The EvalPrediction object received in Trainers compute_metrics function returns an unequal number of label_ids and predictions.
My compute_metrics function given to the Trainer looks like this:
The shapes I print:
And the error message I get:
Does anyone of you have a solution to this? 
What does your data look like? I’m afraid there might have been some labels that were a list concatenated with single labels or something like that.
I found a solution to the problem!
I struggled with doing multi-label classification using the transformers Trainer until I found the following modification of the Trainer class here: Trainer
For some reason I also modified the Trainer for a multi class classification problem I have:
First, I discovered that there is no need for doing that, because the Trainer already does multi class by default 
The problem seemed to be caused by my multi-class Trainer modification 
