import { ch_getbufnr } from "https://deno.land/x/denops_std@v5.1.0/function/vim/mod.ts";
Get the buffer number that {handle} is using for String {what}. {handle} can be a Channel or a Job that has a Channel. {what} can be "err" for stderr, "out" for stdout or empty for socket output. Returns -1 when there is no buffer.
Can also be used as a method:
GetChannel()->ch_getbufnr(what)