make parent fault filter chainable

[chrisbc]

• closes Feature: make FilterParentFaultIds a ChainableSet subclass #51
• added symmetric difference
• some small docstring fixes
• also closes rupture ID type inconsistency #57 with test. In an ideal world the typing for ChainableSet would support this. eg -> ChainableSet[int]

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.29%. Comparing base (f635311) to head (171973f).
Report is 2 commits behind head on pre-release.

Additional details and impacted files

@@             Coverage Diff              @@
##           pre-release      #66   +/-   ##
============================================
  Coverage        99.29%   99.29%           
============================================
  Files               23       23           
  Lines             1273     1280    +7     
  Branches            62       63    +1     
============================================
+ Hits              1264     1271    +7     
  Misses               8        8           
  Partials             1        1           

Flag	Coverage Δ
unittests	99.29% <100.00%> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.