The Geometry Attribute feature can reduce the amount of file cache and make it runs faster for Top node, but how can I work with this attribute with Python node. Is it just for the Invoke node and the Geometry Import node?
Thank you.

Currently it's only usable by the Invoke and Geometry Import, and as an output of a TOP Geometry network. Better access to work item geometry data is on my list of things to tackle for the next release, and it should be possible to backport any improvements to 18.0 once they're implemented.