The fixture docstrings in this file intentionally end continuation
prompt lines (e.g. "   ....:     ") with trailing whitespace, which
IPython's ipdoctest parser requires to recognize a blank continuation
line. The pre-commit-hooks "trailing-whitespace" hook doesn't honor
"# fmt: off" and strips that whitespace, which is what broke the
pre-commit autoupdate PR (#15321): once darker/pre-commit-hooks were
bumped and the autofix commit ran, the hook rewrote this file and
tests/test_ipunittest.py failed to collect with
"ValueError: line N of the docstring ... lacks blank after ...".