docs: def _m2m_field_data(field, obj):
      """Returns m2m ``field`` as a dict.
  
      Value is an array of related primary keys and some meta information
      for reconstructing objects.
      """
      data = _basic_field_data(field, obj)
      data[Field.TYPE] = FieldType.M2M
      related = field.rel.to
      relation_info = {
          Field.REL_DB_TABLE: related._meta.db_table,
          Field.REL_APP: related._meta.app_label,
          Field.REL_MODEL: related.__name__
      }
      data[Field.REL] = relation_info
      value = data[Field.VALUE]
      value = [x[0] for x in value.values_list('pk')]
      data[Field.VALUE] = value
      return data