The CI tests are failing with sphinx-autodoc-typehints 1.21.0 and above with this build error:

Extension error (sphinx_autodoc_typehints):
Handler <function process_docstring at 0x7febbe52b9d0> for event 'autodoc-process-docstring' threw an exception (exception: )

A temporary version pin #1017 has been put in, but we need to figure out a solution for the newer versions.