code: def obtain_all_bond_lengths(sp1, sp2, default_bl=None):
      
      if isinstance(sp1, Element):
          sp1 = sp1.symbol
      if isinstance(sp2, Element):
          sp2 = sp2.symbol
      syms = tuple(sorted([sp1, sp2]))
      if syms in bond_lengths:
          return bond_lengths[syms].copy()
      elif default_bl is not None:
          return {1: default_bl}
      else:
          raise ValueError("No bond data for elements {} - {}".format(*syms))
docs: Obtain bond lengths for all bond orders from bond length database
  
      Args:
          sp1 (Specie): First specie.
          sp2 (Specie): Second specie.
          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.
  
      Return:
          A dict mapping bond order to bond length in angstrom