Thank you very much for this cool open-source project. I encountered the following error during training, which occurred after an epoch was completed. I debugged and printed out img_metas, and the result was [{}], which means it's empty. What could be the problem?

Thank you very much for this cool open-source project. I encountered the following error during training, which occurred after an epoch was completed. I debugged and printed out img_metas, and the result was [{}], which means it's empty. What could be the problem?
