Added type hints and pytest tests

[TolstochenkoDaniil]

#373

[faif]

@TolstochenkoDaniil Can you please fix the linter errors? If it's too much work for all, at least only for the files that you modified.

[TolstochenkoDaniil]

for

@TolstochenkoDaniil Can you please fix the linter errors? If it's too much work for all, at least only for the files that you modified.

I'll check the errors, but tox completed ok before commit
Will do my best

[codecov-commenter]

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Codecov Report

Attention: Patch coverage is 96.42857% with 1 line in your changes missing coverage. Please review.

Project coverage is 33.15%. Comparing base (4fcbf1b) to head (c0677d7).
Report is 66 commits behind head on master.

Files with missing lines	Patch %	Lines
patterns/behavioral/strategy.py	96.42%	1 Missing ⚠️

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Additional details and impacted files

@@            Coverage Diff             @@
##           master     #374      +/-   ##
==========================================
+ Coverage   30.87%   33.15%   +2.28%     
==========================================
  Files          39       39              
  Lines        1286     1306      +20     
==========================================
+ Hits          397      433      +36     
+ Misses        889      873      -16     

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[faif]

Let's create a new issue for the remaining linter errors