[TEST COVERAGE] Improve test coverage of time-series graph submodule

[adam2392]

Signed-off-by: Adam Li [email protected]

Fixes: #52
Towards: #54

Changes proposed in this pull request:

• Add lots of unit-tests for time series graphs and organizes their implementation more
• Adds a preliminary user guide for different causal graphs and highlights the alpha functionality of time-series causal graphs

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[codecov-commenter]

Codecov Report

Merging #37 (51c3283) into main (ba73b32) will increase coverage by 5.28%.
The diff coverage is 86.36%.

@@            Coverage Diff             @@
##             main      #37      +/-   ##
==========================================
+ Coverage   68.98%   74.27%   +5.28%     
==========================================
  Files          27       28       +1     
  Lines        2038     2068      +30     
  Branches      510      527      +17     
==========================================
+ Hits         1406     1536     +130     
+ Misses        526      420     -106     
- Partials      106      112       +6     

Impacted Files	Coverage Δ
pywhy_graphs/classes/cpdag.py	73.46% <ø> (ø)
pywhy_graphs/classes/timeseries/digraph.py	91.30% <ø> (ø)
pywhy_graphs/classes/timeseries/pag.py	78.94% <75.00%> (+31.80%)	⬆️
pywhy_graphs/networkx/classes/mixededge.py	81.45% <76.92%> (+0.03%)	⬆️
pywhy_graphs/classes/timeseries/cpdag.py	87.50% <77.77%> (+42.40%)	⬆️
pywhy_graphs/classes/timeseries/graph.py	82.60% <82.60%> (ø)
pywhy_graphs/classes/pag.py	79.03% <100.00%> (+1.44%)	⬆️
pywhy_graphs/classes/timeseries/base.py	84.89% <100.00%> (+0.25%)	⬆️
pywhy_graphs/classes/timeseries/conversion.py	81.81% <100.00%> (ø)
pywhy_graphs/classes/timeseries/mixededge.py	89.65% <100.00%> (+51.05%)	⬆️
... and 6 more

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