code: def subtract_electron_shells(s1, s2, rel_tol=0.0):
      
  
      diff_shells = []
      for sh1 in s1:
          for sh2 in s2:
              if compare_electron_shells(sh1, sh2, rel_tol=rel_tol):
                  break
          else:
              diff_shells.append(copy.deepcopy(sh1))
  
      return diff_shells
docs: Returns the difference between two lists of electron shells (s1 - s2)
  
      This will remove any shells from s1 that are also in s2, within a tolerance