code: def get_bond_order(self, tol=0.2, default_bl=None):
          
          sp1 = list(self.site1.species.keys())[0]
          sp2 = list(self.site2.species.keys())[0]
          dist = self.site1.distance(self.site2)
          return get_bond_order(sp1, sp2, dist, tol, default_bl)
docs: The bond order according the distance between the two sites
          Args:
              tol (float): Relative tolerance to test.
                  (1 + tol) * the longest bond distance is considered
                  to be the threshold length for a bond to exist.
                  (1 - tol) * the shortest bond distance is considered
                  to be the shortest possible bond length
                  Defaults to 0.2.
              default_bl: If a particular type of bond does not exist,
                  use this bond length as a default value
                  (bond order = 1). If None, a ValueError will be thrown.
          Returns:
              Float value of bond order. For example, for C-C bond in
              benzene, return 1.7.