[Feature] Support Omnisource Dataset

[kennymckormick]

No description provided.

[codecov]

Codecov Report

Merging #294 into master will decrease coverage by 0.02%.
The diff coverage is 86.38%.

@@            Coverage Diff             @@
##           master     #294      +/-   ##
==========================================
- Coverage   85.05%   85.02%   -0.03%     
==========================================
  Files          88       89       +1     
  Lines        5994     6338     +344     
  Branches      983     1033      +50     
==========================================
+ Hits         5098     5389     +291     
- Misses        709      755      +46     
- Partials      187      194       +7     

Flag	Coverage Δ
#unittests	85.02% <86.38%> (-0.03%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
mmaction/apis/inference.py	81.81% <ø> (ø)
mmaction/core/evaluation/accuracy.py	89.85% <ø> (ø)
mmaction/datasets/activitynet_dataset.py	95.04% <ø> (ø)
mmaction/datasets/audio_dataset.py	83.78% <ø> (ø)
mmaction/datasets/audio_feature_dataset.py	83.78% <ø> (ø)
mmaction/datasets/base.py	63.07% <ø> (ø)
mmaction/datasets/builder.py	48.71% <ø> (ø)
mmaction/datasets/hvu_dataset.py	67.56% <ø> (ø)
mmaction/datasets/rawframe_dataset.py	82.45% <ø> (ø)
mmaction/datasets/video_dataset.py	82.53% <ø> (ø)
... and 29 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update d6f76cd...d199a8e. Read the comment docs.

[innerlee]

for paths and file operations, we prefer the dedicated functions