Add unit tests for general_utils.get_scc_from_tuples.
Add unit tests for general_utils.get_scc_from_tuples.

probcomp/crosscat,mit-probabilistic-computing-project/crosscat,mit-probabilistic-computing-project/crosscat,probcomp/crosscat,mit-probabilistic-computing-project/crosscat,probcomp/crosscat,probcomp/crosscat,probcomp/crosscat,mit-probabilistic-computing-project/crosscat,mit-probabilistic-computing-project/crosscat,probcomp/crosscat,probcomp/crosscat,mit-probabilistic-computing-project/crosscat,mit-probabilistic-computing-project/crosscat,probcomp/crosscat