The plus_first and plus_second semirings are very useful for writing algorithms that only care about the nonzero structure of the matrix because they can work on any user matrix without copy or modification.

The documented list of semirings, https://python-graphblas.readthedocs.io/en/stable/user_guide/operators.html#semirings , does not include these, nor could I find them in the code anywhere.

I only found them when I saw pygraphblas had them and just tried the name. They're very useful! I think they belong in the docs.