Tests fail to run: ImportError: attempted relative import with no known parent package

ImportError while importing test module '/usr/ports/misc/py-pymatreader/work-py39/pymatreader-0.0.32/tests/test_pymatreader.py'.
Hint: make sure your test modules/packages have valid Python names.
Traceback:
/usr/local/lib/python3.9/importlib/__init__.py:127: in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
tests/test_pymatreader.py:35: in <module>
    from .helper_functions import assertDeepAlmostEqual, sanitize_dict, \
E   ImportError: attempted relative import with no known parent package
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! Interrupted: 1 error during collection !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
====================================================================================== 1 error in 0.80s =======================================================================================

Version: 0.0.32

Python-3.9

FreeBSD 13.2