Add backwards compatibility for igraph subgraph

[maksymiuks]

No description provided.

[codecov]

Codecov Report

Attention: Patch coverage is 75.00000% with 1 line in your changes missing coverage. Please review.

Project coverage is 90.27%. Comparing base (a8448d8) to head (13b22a4).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
R/task_graph.R	75.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #59      +/-   ##
==========================================
- Coverage   90.32%   90.27%   -0.05%     
==========================================
  Files          21       21              
  Lines        1468     1471       +3     
==========================================
+ Hits         1326     1328       +2     
- Misses        142      143       +1     

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