docs: def gen_reciprocals(self, append=False):
          """ Generate reciprocal configurations, sort by AB, and optionally
          append to configurations.
  
          Parameters
          ----------
          append : bool
              Append reciprocals to configs (the default is False).
  
          Examples
          --------
          >>> cfgs = ConfigManager(nr_of_electrodes=5)
          >>> nor = cfgs.gen_dipole_dipole(skipc=0)
          >>> rec = cfgs.gen_reciprocals(append=True)
          >>> print(cfgs.configs)
          [[1 2 3 4]
           [1 2 4 5]
           [2 3 4 5]
           [3 4 1 2]
           [4 5 1 2]
           [4 5 2 3]]
          """
          # Switch AB and MN
          reciprocals = self.configs.copy()[:, ::-1]
          reciprocals[:, 0:2] = np.sort(reciprocals[:, 0:2], axis=1)
          reciprocals[:, 2:4] = np.sort(reciprocals[:, 2:4], axis=1)
          # # Sort by current dipoles
          ind = np.lexsort((reciprocals[:, 3], reciprocals[:, 2],
                            reciprocals[:, 1], reciprocals[:, 0]))
          reciprocals = reciprocals[ind]
  
          if append:
              self.configs = np.vstack((self.configs, reciprocals))
          return reciprocals