docs: def change_wavelength(self, wavelength):
          '''
          Changes the wavelength of the structure.
  
          This will affect the mode solver and potentially
          the refractive indices used (provided functions
          were provided as refractive indices).
  
          Args:
              wavelength (float): The new wavelength.
          '''
          for name, slab in self.slabs.items():
              const_args = slab._const_args
              mat_args = slab._mat_params
  
              const_args[8] = wavelength
  
              s = Slab(*const_args)
              for mat_arg in mat_args:
                  s.add_material(*mat_arg)
  
              self.slabs[name] = s
  
          self._wl = wavelength