docs: def contribute_to_class(self, process, fields, name):
          """Register this field with a specific process.
  
          :param process: Process descriptor instance
          :param fields: Fields registry to use
          :param name: Field name
          """
          # Use order-preserving definition namespace (__dict__) to respect the
          # order of GroupField's fields definition.
          for field_name in self.field_group.__dict__:
              if field_name.startswith('_'):
                  continue
  
              field = getattr(self.field_group, field_name)
              field.contribute_to_class(process, self.fields, field_name)
  
          super().contribute_to_class(process, fields, name)