code: def find_max_rad_npnp(self):
          
          max_rad = 0
          max_npnp = 0
          for res, atoms in self.items():
              if res != 'KEY':
                  for atom, ff_params in self[res].items():
                      if max_rad < ff_params[1]:
                          max_rad = ff_params[1]
                      if max_npnp < ff_params[4]:
                          max_npnp = ff_params[4]
          return max_rad, max_npnp
docs: Finds the maximum radius and npnp in the force field.
  
          Returns
          -------
          (max_rad, max_npnp): (float, float)
              Maximum radius and npnp distance in the loaded force field.