add instructions of installing coco api

README.md

@@ -17,8 +17,12 @@ transformers==4.57.3 (with Qwen3 series)
 
 
 ### Prepare Dataset
-5. Download [dataset](https://huggingface.co/datasets/ayh015/HICO-Det_Halpe_HAKE).
-6. Organize dataset, your directory tree of dataset should look like this (there maybe extra files.):
+5. Install COCO API:
+   ```
+   pip install pycocotools
+   ```
+6. Download [dataset](https://huggingface.co/datasets/ayh015/HICO-Det_Halpe_HAKE).
+7. Organize dataset, your directory tree of dataset should look like this (there maybe extra files.):
    ```
    {DATA_ROOT}
    |-- Annotation