/usr/lib/python3-escript/esys/downunder/ is in python3-escript 5.1-5.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/python3-escript/esys/downunder/__init__.py
/usr/lib/python3-escript/esys/downunder/coordinates.py
/usr/lib/python3-escript/esys/downunder/costfunctions.py
/usr/lib/python3-escript/esys/downunder/datasources.py
/usr/lib/python3-escript/esys/downunder/dcresistivityforwardmodeling.py
/usr/lib/python3-escript/esys/downunder/domainbuilder.py
/usr/lib/python3-escript/esys/downunder/forwardmodels/
/usr/lib/python3-escript/esys/downunder/forwardmodels/__init__.py
/usr/lib/python3-escript/esys/downunder/forwardmodels/acoustic.py
/usr/lib/python3-escript/esys/downunder/forwardmodels/base.py
/usr/lib/python3-escript/esys/downunder/forwardmodels/dcresistivity.py
/usr/lib/python3-escript/esys/downunder/forwardmodels/gravity.py
/usr/lib/python3-escript/esys/downunder/forwardmodels/magnetic.py
/usr/lib/python3-escript/esys/downunder/forwardmodels/magnetotelluric2d.py
/usr/lib/python3-escript/esys/downunder/forwardmodels/pressure.py
/usr/lib/python3-escript/esys/downunder/forwardmodels/subsidence.py
/usr/lib/python3-escript/esys/downunder/inversioncostfunctions.py
/usr/lib/python3-escript/esys/downunder/inversions.py
/usr/lib/python3-escript/esys/downunder/magtel1d.py
/usr/lib/python3-escript/esys/downunder/magtel2d.py
/usr/lib/python3-escript/esys/downunder/mappings.py
/usr/lib/python3-escript/esys/downunder/minimizers.py
/usr/lib/python3-escript/esys/downunder/regularizations.py
/usr/lib/python3-escript/esys/downunder/seismic.py
/usr/lib/python3-escript/esys/downunder/splitinversioncostfunctions.py
/usr/lib/python3-escript/esys/downunder/splitminimizers.py
/usr/lib/python3-escript/esys/downunder/splitregularizations.py