* clean up unused imports in examples
* enable unused import checking in examples
* lint
* ignore F541 and F841 - focus on unused imports only
* clean up
* restore tinygrad.frontend.torch for TINY_BACKEND
* tiny change
* different way to write torch backend
* both backends
* more work
* simpler code
* more work
* test both
* imply unwrap/wrap
* FORWARD_ONLY=1 TINY_BACKEND=1 python3 test/test_ops.py TestOps.test_add works
* ready to start making test_ops work in torch backend
* backward pass, TINY_BACKEND=1 python3 test/test_ops.py TestOps.test_add works
* FORWARD_ONLY=1 TINY_BACKEND=1 python3 test/test_ops.py TestOps.test_simple_conv2d works
* matmul backward is broken with as_strided