code: def MD_ConfigsPermutate(df_md):
      
      g_current_injections = df_md.groupby(['a', 'b'])
      ab = np.array(list(g_current_injections.groups.keys()))
      config_mgr = ConfigManager(nr_of_electrodes=ab.max())
      config_mgr.gen_configs_permutate(ab, silent=True)
      return config_mgr.configs
docs: Given a MD DataFrame, return a Nx4 array which permutes the current
      injection dipoles.