FilterDualIter - analog `map` (in terms of map-filter-reduce pattern) please avoid reading from Disk/DB more elements and then filter them.

FilterUnaryIter - analog `map` (in terms of map-filter-reduce pattern) please avoid reading from Disk/DB more elements and then filter them.

IntersectIter.

PaginatedIter - for remote-list pagination Rationale: If an API does not support pagination from the start, supporting it later is troublesome because adding pagination breaks the API's behavior.

PairsWithErrorIter - return N, keys and then error.

TransformDualIter - analog `map` (in terms of map-filter-reduce pattern).

UnionKVIter - merge 2 kv.Pairs streams to 1 in lexicographically order 1-st stream has higher priority - when 2 streams return same key.

UnionUnary.

Dual - return 2 items - usually called Key and Value (or `k` and `v`) Example: for s.HasNext() { k, v, err := s.Next() if err != nil { return err } }.

Unary - return 1 item.

internal types.

internal types.