Update dataset README

README.md

@@ -54,8 +54,11 @@ pip install lance huggingface_hub
 ```python
 import lance
 
-# arxiv（762 条）
-pdfs   = lance.dataset("hf://datasets/KuoKuoYeah/dcd-pdf-demo/arxiv/pdfs.lance")
+# 按需拉取，不下载全部 974 MB
+pdfs = lance.dataset("hf://datasets/KuoKuoYeah/dcd-pdf-demo/arxiv/pdfs.lance")
+print(pdfs.count_rows())
+sample = pdfs.take([0, 1, 2]).to_pydict()
+
 labels = lance.dataset("hf://datasets/KuoKuoYeah/dcd-pdf-demo/arxiv/pdf_labels.lance")
 print(labels.schema)
 ```