With variables it's much easier to format GraphQL queries and mutations. See the usage documentation of the used gql library:
https://github.com/graphql-python/gql/blob/master/docs/usage/variables.rst

Probably pretty simple to add by adding variable_values to the execute method and pass it on to the GQL request:

def execute(self, request: str, variable_values: Dict[str, Any], *args: Any, **kwargs: Any) -> Any:
  parsed_document = self._gql(request)
  parsed_document.variable_values = variable_values