Tests and methods for individual parents

[benjeffery]

Closes #1135

I've been through quite closely to check for extra bits and pieces.

[codecov]

Codecov Report

Merging #1153 (b839c7a) into main (93a3fd8) will increase coverage by 0.08%.
The diff coverage is 94.73%.

@@            Coverage Diff             @@
##             main    #1153      +/-   ##
==========================================
+ Coverage   93.65%   93.73%   +0.08%     
==========================================
  Files          26       26              
  Lines       21236    21254      +18     
  Branches      900      902       +2     
==========================================
+ Hits        19888    19922      +34     
+ Misses       1311     1294      -17     
- Partials       37       38       +1     

Flag	Coverage Δ
c-tests	92.52% <ø> (+0.16%)	⬆️
lwt-tests	92.78% <ø> (ø)
python-c-tests	94.89% <94.73%> (-0.01%)	⬇️
python-tests	98.62% <94.73%> (-0.02%)	⬇️

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Impacted Files	Coverage Δ
python/tskit/trees.py	97.42% <90.90%> (-0.05%)	⬇️
python/tskit/tables.py	99.60% <100.00%> (+<0.01%)	⬆️
python/tskit/util.py	100.00% <100.00%> (ø)
c/tskit/tables.c	90.81% <0.00%> (+0.30%)	⬆️

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[jeromekelleher]

Looks great, thanks for slogging through this one.

Just looks like we're missing a quick test for the text format?

[benjeffery]

Looks great, thanks for slogging through this one.

Just looks like we're missing a quick test for the text format?

I've added #1175 as all the text parse methods need them, which seemed beyond this PR.