code: def _validate_property_names(class_name, properties):
      
      for property_name in properties:
          if not property_name or property_name.startswith(ILLEGAL_PROPERTY_NAME_PREFIXES):
              raise IllegalSchemaStateError(u'Class "{}" has a property with an illegal name: '
                                            u'{}'.format(class_name, property_name))
docs: Validate that properties do not have names that may cause problems in the GraphQL schema.