default UnframedGrpcStatusMappingFunction orElse(UnframedGrpcStatusMappingFunction other) {
        requireNonNull(other, "other");
        if (this == other) {
            return this;
        }
        return (ctx, status, cause) -> {
            final HttpStatus httpStatus = apply(ctx, status, cause);
            if (httpStatus != null) {
                return httpStatus;
            }
            return other.apply(ctx, status, cause);
        };
    }
Returns a composed {@link UnframedGrpcStatusMappingFunction} that applies {@code this} first and
the specified {@code other} later if {@code this} returns {@code null}.
grpc/src/main/java/com/linecorp/armeria/server/grpc/UnframedGrpcStatusMappingFunction.java