Added Mirror Formulae Equation (#9717)

* Python mirror_formulae.py is added to the repository

* Changes done after reading readme.md

* Changes for running doctest on all platforms

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Change 2 for Doctests

* Changes for doctest 2

* updating DIRECTORY.md

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