What is the meaning of 'category_id' in each annotation?

[hqhQAQ]

I notice that each annotation has a field named 'category_id', the total number of all unique 'category_id' is 40, consistently in 'train.json' and 'test.json'. I wonder whether 'category_id' is the id of the object part, but it seems that the original paper does not mention it.

[hqhQAQ]

I validate my assumption in the 'categories' field in the annotation file, which include the names of 40 object part categories.
This issue can be closed.

[yongliu20]

Hi, I can't find the annotation file that describes the names of 40 object part categories. Could you provide the category name-id pair? Thanks.