Extracted from #31071 (comment)

check_getitem() is somewhat different from the other check_* methods. Both do some form of input validation and error out with a nice error message. But while the check_* only do an assertion, check_getitem() retrieves a value. It's also the only function that has a return value.

A function named check_... should not return something (or if it returns something, it'd intuitively return the result of the check). I therefore propose that re rename check_getitem() to getitem_checked() or similar.