Dataset Downloading for Specific Benchmark

Hello, all,
I am using egoexo -o ./egoexo --benchmarks relations to download the data, but received Provided invalid benchmarks: {‘relations’}. But from the help information, I think it is a valid benchmark. And I can download data with egoexo -o ./egoexo. Is there anybody who can help me with this issue? Thank you so much in advance!