[FR] Report labels along with progress of delegated operations?

[brimoor]

Possible TODO

• Add ProgressBar.start_msg property in voxel51-eta
• Update all usages of ProgressBar in fiftyone to use start_msg rather than separate logging messages
• Update the progress callbacks introduced in Report progress of delegated operations #101 PR to use ctx.set_progress(label=pb.start_msg, progress=pb.progress)

Why? This would provide a bit more info to users about what is actually happening in our builtin operations. This may be especially useful if there is a builtin operation that uses multiple progress bars, in which case the naive implementation may involve two separate progress bars that "reset" progress back to 0% when the second progress bar starts.

One operation that could "want" to have multiple progress bars is @voxel51/io/import_samples when uploading media to a new location before adding samples:

fiftyone-plugins/plugins/io/__init__.py

Line 957 in 3bde4f8

fos.copy_files(inpaths, outpaths)

Currently if the upload step happens, there is no progress bar, so the progress indicator in #101 is not particularly useful in this case as it will sit at 0% for awhile and then rapidly jump to 100% as add_samples() is a faster operation than copy_files().

An alternative to the double progress bar problem is this pattern:

progress1 = lambda pb: ctx.set_progress(progress=0.5 * pb.progress)
progress2 = lambda pb: ctx.set_progress(progress=0.5 + 0.5 * pb.progress)