fixed graph topology priority

examples/example_utils.py

examples/scalar_advection/scalar_advection.py

examples/taylor_green/taylor_green.py

examples/taylor_green/taylor_green_cpu.py

hysop/backend/device/opencl/opencl_kernel_autotuner.py

...ckend/device/opencl/operator/directional/advection_dir.py

hysop/backend/host/fortran/operator/scales_advection.py

hysop/core/graph/computational_operator.py

hysop/core/graph/graph_builder.py

hysop/core/mpi/redistribute.py

hysop/fields/cartesian_discrete_field.py

hysop/operator/base/advection_dir.py

hysop/operator/base/memory_reordering.py

hysop/operator/base/min_max.py

hysop/operator/base/redistribute_operator.py

hysop/operator/base/transpose_operator.py

hysop/operator/hdf_io.py

hysop/operator/memory_reordering.py

hysop/operator/transpose.py

hysop/tools/contexts.py