[Feature] Support for the situation that an uncertain number of samples of the same class in one image

[lishuwei10]

What is the feature?

I want to apply MMPose to fields other than human pose estimation. The specific difference is that the number of keypoints in some categories is not one and cannot be determined. The current code for Dataset usually arranges keypoints by category (such as the most commonly used coco dataset), which results in only one or no samples for a category of keypoints being allowed. How should I solve this problem?

Any other context?

No response