style(client) polish code style

[duhenglucky]

What is the purpose of the change

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Brief changelog

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Verifying this change

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[codecov-io]

Codecov Report

Merging #72 into ctypes will increase coverage by 1.79%. The diff coverage is 67.85%.

@@            Coverage Diff             @@
##           ctypes      #72      +/-   ##
==========================================
+ Coverage    80.4%   82.19%   +1.79%     
==========================================
  Files           4        4              
  Lines         541      528      -13     
==========================================
- Hits          435      434       -1     
+ Misses        106       94      -12

Impacted Files	Coverage Δ
rocketmq/client.py	66.01% <67.85%> (+2.81%)	:arrow_up:

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