Coverage: 99.48% (+0.0001%) from 99.48% when pulling 92da690 on eriknw:chain_wait into ed6f3ba on python-graphblas:main.

This raises the question whether we should do the same for build, clear, and/or resize.

Nevermind, expressions shouldn't (and don't) have build/clear/resize, so these shouldn't return self. expr.wait() doesn't actually modify the object, so having val = expr.wait() can be a nice shorthand for val = expr.new().wait().