Are finite binary relations as subsets of Cartesian product implemented in Sage? I am interested in taking set-theoretic operations, finding composition and inverse, checking properties such as reflexivity and antisymmetry. I found a report here, but I am not sure if it made its way into version 8.5. If so, is there documentation and examples? By doing search_src("binaryrelation") I also found functions IsBinaryRelation, IsReflexiveBinaryRelation, etc. in libs/gap/gap_functions.py, but I am not sure how to use them.