Function keyval_inner_join

pub fn keyval_inner_join<'s, 'i, 'k, 'v, K: Ord + 'k, V: 'v>(
    sequences: &'s mut [Option<impl IntoIterator<Item = KeyVal<K, V>> + 'i>],
) -> Option<Box<dyn Iterator<Item = KeyVal<K, Vec<V>>> + 'i>>
where
    's: 'i,
    'k: 'i,
    'v: 'i,

Join any number of sequences of KeyVal, ordered by KeyVal.key. Only keys present in all sequences are preserved. I.e. the resulting sequence has Vecs of the same number of elements as sequences. Returns None if sequences is empty.