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* :func:`Indexer` renamed to :func:`index_fields`.
* :meth:`Sector.get_args` deprecated in favor of using
:func:`get_field_args`.
* Added :class:`Histogrammer` and :class:`FieldHistogrammer`.
* Added :meth:`Projector.tensor_to_pol`, :meth:`Projector.pol_to_tensor`,
and :meth:`PowerSpectra.gw_polarization`.
* Various improvements and bug fixes.