code: def ndxlist(self):
          
          return [{'name': name, 'natoms': len(atomnumbers), 'nr': nr+1} for
                  nr,(name,atomnumbers) in enumerate(self.items())]
docs: Return a list of groups in the same format as  :func:`gromacs.cbook.get_ndx_groups`.
  
          Format:
             [ {'name': group_name, 'natoms': number_atoms, 'nr':  # group_number}, ....]