code: def are_equal(self, sp1, sp2):
          
          set1 = set(sp1.element_composition.values())
          set2 = set(sp2.element_composition.values())
          if set1 == set2:
              return True
          else:
              return False
docs: Args:
              sp1: First species. A dict of {specie/element: amt} as per the
                  definition in Site and PeriodicSite.
              sp2: Second species. A dict of {specie/element: amt} as per the
                  definition in Site and PeriodicSite.
  
          Returns:
              True if sets of occupancies (amt) are equal on both sites.