When assigning instance attributes in Maya, they can be named like Primvars, where controls are found on the shape node. Or as attributes found on the transform node and variable per instance.

 

Example commands:

rfm2.ui.user_attrs.user_attrs_add(data_attr, nodelist, pdict) -> add to one or more nodes

rfm2.ui.user_attrs.user_attrs_del(data_attr, nodelist, attrlist) -> delete from one or more nodes

rfm2.ui.user_attrs.user_attrs(node) -> list all user attributes