code: def get_next_step(self):
          
          is_raster = is_raster_layer(self.parent.layer)
          subcategory = self.parent.step_kw_subcategory.selected_subcategory()
          has_unit = subcategory.get('units') or subcategory.get(
              'continuous_hazard_units')
          selected_layer_mode = self.selected_layermode()
  
          # continuous
          if selected_layer_mode == layer_mode_continuous and has_unit:
              new_step = self.parent.step_kw_unit
          # no unit and vector
          elif not is_raster:
              new_step = self.parent.step_kw_field
          # no unit and raster
          elif is_raster:
              new_step = self.parent.step_kw_multi_classifications
          else:
              raise InvalidWizardStep
  
          return new_step
docs: Find the proper step when user clicks the Next button.
  
          :returns: The step to be switched to
          :rtype: WizardStep instance or None