Apply fixes from StyleCI

[guanguans]

This pull request applies code style fixes from an analysis carried out by StyleCI.

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For more information, click here.

[codecov-io]

Codecov Report

Merging #20 into master will not change coverage by %.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master      #20   +/-   ##
=========================================
  Coverage     67.18%   67.18%           
  Complexity       36       36           
=========================================
  Files             1        1           
  Lines            64       64           
=========================================
  Hits             43       43           
  Misses           21       21           

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