[WIP] Functions to retrieve fragments of realspace Hamiltonians

[willjmax]

realspace Hamiltonian functions

[github-actions]

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.60%. Comparing base (3811724) to head (301d12e).

Additional details and impacted files

@@                Coverage Diff                @@
##           realspace-states    #7036   +/-   ##
=================================================
  Coverage             99.60%   99.60%           
=================================================
  Files                   488      488           
  Lines                 46622    46622           
=================================================
  Hits                  46439    46439           
  Misses                  183      183           

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