import dgl.data
dataset = dgl.data.CoraGraphDataset()
错误：
Downloading /Users/vinayakbali/.dgl/cora_v2.zip from https://data.dgl.ai/dataset/cora_v2.zip...
download failed, retrying, 2 attempts left
Downloading /Users/vinayakbali/.dgl/cora_v2.zip from https://data.dgl.ai/dataset/cora_v2.zip...
download failed, retrying, 1 attempt left
Downloading /Users/vinayakbali/.dgl/cora_v2.zip from https://data.dgl.ai/dataset/cora_v2.zip...
SSLError: HTTPSConnectionPool(host='data.dgl.ai', port=443): Max retries exceeded with url: /dataset/cora_v2.zip (Caused by SSLError(SSLCertVerificationError(1, '[SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed: unable to get local issuer certificate (_ssl.c:1056)')))
手动下载文件并放在.dgl目录下。另一种选择是读取手动下载的文件。至少如何做到这一点？