code: def filter_by_widget(self, widget_type):
          
          self._check_layout_and_form()
          layout_field_names = self.layout.get_field_names()
  
          # Let's filter all fields with widgets like widget_type
          filtered_fields = []
          for pointer in layout_field_names:
              if isinstance(self.form.fields[pointer[1]].widget, widget_type):
                  filtered_fields.append(pointer)
  
          return LayoutSlice(self.layout, filtered_fields)
docs: Returns a LayoutSlice pointing to fields with widgets of `widget_type`