def validate_metadata_token(self, claims, endpoint):
        """
        If the token endpoint is used in the grant type, the value of this
        parameter MUST be the same as the value of the "grant_type"
        parameter passed to the token endpoint defined in the grant type
        definition.
        """
        self._grant_types.extend(endpoint._grant_types.keys())
        claims.setdefault("token_endpoint_auth_methods_supported", ["client_secret_post", "client_secret_basic"])

        self.validate_metadata(claims, "token_endpoint_auth_methods_supported", is_list=True)
        self.validate_metadata(claims, "token_endpoint_auth_signing_alg_values_supported", is_list=True)
        self.validate_metadata(claims, "token_endpoint", is_required=True, is_url=True)
If the token endpoint is used in the grant type, the value of this
        parameter MUST be the same as the value of the "grant_type"
        parameter passed to the token endpoint defined in the grant type
        definition.