docs: def to_schema(self):
          """Return field schema for this field."""
          schema = super().to_schema()
          if self.disabled is not None:
              schema['disabled'] = self.disabled
          if self.collapsed is not None:
              schema['collapsed'] = self.collapsed
  
          group = []
          for field in self.fields.values():
              group.append(field.to_schema())
          schema['group'] = group
  
          return schema