noted today that h3 is now at 4.0. the 4.0 API changes the name of methods. straight off the top of the documentation, the 3.x geo_to_h3 and h3_to_geo functions have been renamed latlng_to_cell and cell_to_latlng.
a quick immediate update is to restrict h3 versions to 3.x in our pyproject.toml, and long-term, we should update to the latest version or provide an abstraction to support both versions.
note: most h3 functionality occurs in h3_ops.py.