Well, you might have duplicates in a certain batch, but it is strange to have it for a single sample.
Let’s say you have a batch of two samples with the following labels:
batch[
sample0: [Adventure, Action]
sample1: [Adventure, Action, Romance]
]

This example is perfectly fine. The corresponsing target tensors could look like this (depending on the mapping between the genres and the class index):
[[2, 1],
 [2, 1, 5]]

It’s still a bit strange for me to see the same label (Adventure) for the same sample.
This would mean the example from above could look like this:
sample0: [Adventure, Adventure, Action] - [2, 2, 1]

Would you like to ignore duplicates for these samples or does it have any meaning?