Fix/code cleanup

[vinitkumar]

Update code as per warnings by different code quality tools

https://github.com/vinitkumar/json2xml/security/code-scanning

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 70.00000% with 3 lines in your changes missing coverage. Please review.

Project coverage is 95.07%. Comparing base (577ad37) to head (f655a8b). Report is 26 commits behind head on master.

Files with missing lines	Patch %	Lines
json2xml/dicttoxml.py	66.66%	3 Missing :warning:

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #204      +/-   ##
==========================================
- Coverage   95.53%   95.07%   -0.46%     
==========================================
  Files           6        6              
  Lines         582      589       +7     
==========================================
+ Hits          556      560       +4     
- Misses         26       29       +3     

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