Fix Wandblogger import error

[gogoduan]

• I have marked all applicable categories:
  • exception-raising fix
  • algorithm implementation fix
  • documentation modification
  • new feature
• I have reformatted the code using make format (required)
• I have checked the code using make commit-checks (required)
• If applicable, I have mentioned the relevant/related issue(s)
• If applicable, I have listed every items in this Pull Request below

[codecov-commenter]

Codecov Report

Merging #562 (9fee0b9) into master (df3d7f5) will decrease coverage by 0.06%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #562      +/-   ##
==========================================
- Coverage   93.85%   93.78%   -0.07%     
==========================================
  Files          64       64              
  Lines        4376     4376              
==========================================
- Hits         4107     4104       -3     
- Misses        269      272       +3     

Flag	Coverage Δ
unittests	93.78% <ø> (-0.07%)	⬇️

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Impacted Files	Coverage Δ
tianshou/policy/modelfree/trpo.py	88.52% <0.00%> (-4.92%)	⬇️

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