  The HistFactory p.d.f. template is per-se independent of its implementation
in ROOT and it is useful to be able to run statistical analysis outside of the
ROOT, RooFit, RooStats framework. pyhf is a pure-Python implementation of that
statistical model for multi-bin histogram-based analysis and its interval
estimation is based on the asymptotic formulas of "Asymptotic formulae for
likelihood-based tests of new physics". pyhf supports modern computational
graph libraries such as TensorFlow, PyTorch, and JAX in order to make use of
features such as auto-differentiation and GPU acceleration. In addition, pyhf's
JSON serialization specification for HistFactory models has been used to
publish 23 full probability models from published ATLAS collaboration analyses
to HEPData.
