Reduce dependency on finmag by copying helper context manager directly into utils/oommf_calculator.py
Reduce dependency on finmag by copying helper context manager directly into utils/oommf_calculator.py

ryanpepper/oommf-python,ryanpepper/oommf-python,fangohr/oommf-python,fangohr/oommf-python,ryanpepper/oommf-python,ryanpepper/oommf-python,fangohr/oommf-python