intermediate stage; broken

nifty6/domains/lm_space.py

nifty6/domains/rg_space.py

nifty6/extra.py

nifty6/field.py

nifty6/linearization.py

nifty6/multi_field.py

nifty6/operators/energy_operators.py

nifty6/operators/simple_linear_operators.py

test/test_field.py

test/test_operators/test_fft_operator.py

test/test_operators/test_harmonic_transform_operator.py