Question about contributing a TODO implementation in Tensor::Slice

[michal-bakshi]

I'm starting to contribute to Open3D and noticed a TODO in the following function:

cpp/open3d/core/Tensor.cpp
Tensor Tensor::Slice(int64_t dim, int64_t start, int64_t stop, int64_t step) const

The TODO mentions supporting negative steps.
I went ahead and implemented this behavior and also added tests to cover the new functionality.

Before opening a pull request, I wanted to ask:
Is it common to open a PR directly for an existing TODO, or is it better practice to first open an issue and then link the PR to it?