Function map6

pub fn map6<'a, F, _1, _2, _3, _4, _5, _6, NewDecodesTo>(
    func: F,
    _1: BoxDecoder<'a, _1>,
    _2: BoxDecoder<'a, _2>,
    _3: BoxDecoder<'a, _3>,
    _4: BoxDecoder<'a, _4>,
    _5: BoxDecoder<'a, _5>,
    _6: BoxDecoder<'a, _6>,
) -> BoxDecoder<'a, NewDecodesTo>
where
    F: Fn(_1, _2, _3, _4, _5, _6) -> NewDecodesTo + 'a + Send + Sync,
    NewDecodesTo: 'a,
    _1: 'a,
    _2: 'a,
    _3: 'a,
    _4: 'a,
    _5: 'a,
    _6: 'a,