What is a Variable? Why did it exist as a wrapper in the first place? Why did it get removed? How did we remove it? What are some of the lingering consequences of its removal?

Further reading:

• The release notes of PyTorch 0.4 do a good job explaining the user visible consequences of the removal, at the time, including how we "simulate" concepts on Variable that don't make sense anymore https://pytorch.org/blog/pytorch-0_4_0-migration-guide/
• Part 1: Removal of Variable wrapper in C++ https://github.com/pytorch/pytorch/pull/17072
• Part 2: Merge of Variable and Tensor types in C++ https://github.com/pytorch/pytorch/pull/28620