presto-main/src/main/java/io/prestosql/operator/window/FirstValueFunction.java/FirstValueFunction/FirstValueFunction
class FirstValueFunction:    public FirstValueFunction(List<Integer> argumentChannels, boolean ignoreNulls)
    {
        this.argumentChannel = getOnlyElement(argumentChannels);
        this.ignoreNulls = ignoreNulls;
    }