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* Starting with this version, ``crystals`` is licensed under GPLv3.
* General purpose single-crystal structure indexing with the DirAx algorithm has been added: :func:`index_dirax`.
* :meth:`Lattice.scattering_vector` and :meth:`Lattice.miller_indices` now accept tables of reflections/scattering vectors. This calculation is vectorized using NumPy.
* Migration of testing infrastructure to pytest.
* `Support for Python 3.6 and NumPy<1.17 has been dropped <https://numpy.org/neps/nep-0029-deprecation_policy.html>`_