removed strict enum checking, imports cleanup

[rhajek]

Removed strict enum checking.

[codecov-io]

Codecov Report

Merging #19 into master will increase coverage by 0.19%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master      #19      +/-   ##
==========================================
+ Coverage   86.88%   87.08%   +0.19%     
==========================================
  Files          20       20              
  Lines        1533     1556      +23     
==========================================
+ Hits         1332     1355      +23     
  Misses        201      201

Impacted Files	Coverage Δ
influxdb_client/client/__init__.py	100% <100%> (ø)	⬆️
influxdb_client/__init__.py	100% <100%> (ø)	⬆️

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