Bug fix release

This update includes a suite of bug fixes.

• Fix for apply_mask function with single coil data (PR #255)
• New filter function feature for filtering contrasts with a SliceDataset (PR #257).
• Fix for AnnotatedSliceDataset annotation versions (PR #276).
• Fix typecast in varnet (PR #303).
• Fix annotation metadata extraction for AnnotatedSliceDataset (PR #310).
• Fix calculation of y location in AnnotatedSliceDataset (PR #311).

Contributors: @zaccharieramzi @NikolasMorshuis @ad12

Adaptive VarNet Implementation

This release of fastMRI includes PyTorch Lightning modules for the paper On learning adaptive acquisition policies for undersampled multi-coil MRI reconstruction by Bakker et al., to be presented at the upcoming MIDL conference. A list of changes is below:

• Add Adaptive VarNet implementation (PR #205)
• Compatibility for fastMRI+ in SliceDataset (PR #192) - currently in beta.
• Masking API updates (PR #167).
• Various smaller bug fixes and improvements.

Contributors:
@Timsey @luisenp @michaldrozdzal

Packaging fixes, FFT API update

• Includes a fix for packaging that removes fastmri_examples from distributed sources. (#145).
• Updates the FFT API to allow the user to adjust normalizations (#146).

Release to PyPI

This release does not introduce any major changes - it merely includes metadata for publishing the project on PyPI. The creation of this release also tests the GitHub release action.