docs: def labels(self):
          """
          Returns a dictionary containing kink information:
          {index: 'x= mixing_ratio energy= reaction_energy reaction_equation'}.
          E.g., {1: 'x= 0.0 energy = 0.0 Mn -> Mn',
                 2: 'x= 0.5 energy = -15.0 O2 + Mn -> MnO2',
                 3: 'x= 1.0 energy = 0.0 O2 -> O2'}.
          """
          return {j: 'x= ' + str(round(x, 4)) + ' energy in eV/atom = ' +
                     str(round(energy, 4)) + ' ' + str(reaction)
                  for j, x, energy, reaction, _ in self.get_kinks()}