static GraphqlRequest of(String query, @Nullable String operationName,
                             Map<String, Object> variables, Map<String, Object> extensions) {
        requireNonNull(query, "query");
        checkArgument(!query.isEmpty(), "query is empty");
        requireNonNull(variables, "variables");
        requireNonNull(extensions, "extensions");

        return new DefaultGraphqlRequest(query, operationName, variables, extensions);
    }
Returns a newly-created {@link GraphqlRequest} with the specified {@code query}, {@code operationName}
and {@code variables}.
graphql-protocol/src/main/java/com/linecorp/armeria/common/graphql/protocol/GraphqlRequest.java