code: def get_next_step(self):
          
          if self.parent.step_kw_purpose.\
                  selected_purpose() == layer_purpose_hazard:
              new_step = self.parent.step_kw_hazard_category
          else:
              if is_raster_layer(self.parent.layer):
                  new_step = self.parent.step_kw_band_selector
              else:
                  new_step = self.parent.step_kw_layermode
          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