import { Reducer } from "https://deno.land/x/rimbu@1.1.0/stream/mod.ts";
const { Base } = Reducer;
Parameters
flatMapFun: (value: I2, index: number) => StreamSource<I>
import { Reducer } from "https://deno.land/x/rimbu@1.1.0/stream/mod.ts";
const { Base } = Reducer;