code: def clean_update_fields(self, index, update_fields):
          
          search_fields = get_model_index_properties(self, index)
          clean_fields = [f for f in update_fields if f in search_fields]
          ignore = [f for f in update_fields if f not in search_fields]
          if ignore:
              logger.debug(
                  "Ignoring fields from partial update: %s",
                  [f for f in update_fields if f not in search_fields],
              )
          for f in clean_fields:
              if not self._is_field_serializable(f):
                  raise ValueError(
                      "'%s' cannot be automatically serialized into a search document property. Please override as_search_document_update.",
                      f,
                  )
          return clean_fields
docs: Clean the list of update_fields based on the index being updated.\
  
          If any field in the update_fields list is not in the set of properties
          defined by the index mapping for this model, then we ignore it. If
          a field _is_ in the mapping, but the underlying model field is a
          related object, and thereby not directly serializable, then this
          method will raise a ValueError.