fix no y_dict handle

[senwu]

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Checklist

• [x] I have updated the documentation accordingly.
• [x] I have added tests to cover my changes.
• [x] All new and existing tests passed.
• [x] I have updated the CHANGELOG.rst accordingly.

[codecov[bot]]

Codecov Report

Merging #105 (2fb3f14) into master (4a5813e) will decrease coverage by 0.55%. The diff coverage is 65.85%.

@@            Coverage Diff             @@
##           master     #105      +/-   ##
==========================================
- Coverage   85.24%   84.68%   -0.56%     
==========================================
  Files          40       40              
  Lines        1958     1965       +7     
  Branches      418      419       +1     
==========================================
- Hits         1669     1664       -5     
- Misses        173      178       +5     
- Partials      116      123       +7     

Flag	Coverage Δ
unittests	84.68% <65.85%> (-0.56%)	:arrow_down:

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

Impacted Files	Coverage Δ
src/emmental/meta.py	74.75% <ø> (ø)
src/emmental/schedulers/mixed_scheduler.py	91.42% <50.00%> (-8.58%)	:arrow_down:
src/emmental/schedulers/round_robin_scheduler.py	84.78% <50.00%> (-5.70%)	:arrow_down:
src/emmental/schedulers/sequential_scheduler.py	82.92% <50.00%> (-6.27%)	:arrow_down:
src/emmental/data.py	85.84% <68.96%> (+2.51%)	:arrow_up:
src/emmental/model.py	80.60% <70.58%> (-1.98%)	:arrow_down:
src/emmental/learner.py	68.97% <100.00%> (ø)