[P] einx - Tensor Operations in Einstein-Inspired Notation for Python

## What?

[einx](https://github.com/fferflo/einx) is a Python library that allows formulating many tensor operations as concise expressions using Einstein notation. It is inspired by [einops](http://einops.rocks/).

## Why?

Classical index-based notation is often overly complex and lacks readability and expressiveness. einops was introduced in 2018 to address this problem and provide an alternative way of formulating tensor operations by using Einstein-inspired notation.

While einops has transformed the way many researchers write deep learning code, it has focused mainly on few operations (e.g. …

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