presto-main/src/main/java/io/prestosql/operator/window/AbstractWindowFunctionSupplier.java/AbstractWindowFunctionSupplier/AbstractWindowFunctionSupplier
class AbstractWindowFunctionSupplier:    protected AbstractWindowFunctionSupplier(Signature signature, String description)
    {
        this.signature = requireNonNull(signature, "signature is null");
        this.description = description;
    }