Improve and maintain m-separation function

[jaron-lee]

Signed-off-by: Jaron Lee jaron2005@gmail.com

Fixes #43, #44
Closes: #45

Changes proposed in this pull request:

• Implemented support for m-separation with undirected edges
• Fixed a bug in MixedEdgeGraph with only bidirected edges, where incorrect m-separation statements were being returned
• General refactoring and rewriting of documentation for improved clarity

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[codecov-commenter]

Codecov Report

Merging #46 (808f3a4) into main (c243bda) will increase coverage by 0.37%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main      #46      +/-   ##
==========================================
+ Coverage   68.52%   68.90%   +0.37%     
==========================================
  Files          27       27              
  Lines        2005     2029      +24     
  Branches      484      497      +13     
==========================================
+ Hits         1374     1398      +24     
  Misses        526      526              
  Partials      105      105              

Impacted Files	Coverage Δ
..._graphs/networkx/algorithms/causal/m_separation.py	100.00% <100.00%> (ø)

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[adam2392]

LGTM. Just trying to fix the sphinx error

[adam2392]

Thanks @jaron-lee !