Error message

stream.nim

import osproc, streams, strutils, os

let l = ""
let ps = startProcess("/sbin/iwlist", "", ["wlp2s0", "scan"])
let s = outputStream(ps)

while s.readLine(l):
  echo(l)

Error: type mismatch: got <Stream, string>
but expected one of: 
proc readLine(f: File; line: var TaintedString): bool
  first type mismatch at position: 1
  required type: File
  but expression 's' is of type: Stream
proc readLine(f: File): TaintedString
  first type mismatch at position: 1
  required type: File
  but expression 's' is of type: Stream
proc readLine(s: Stream): TaintedString
  first type mismatch at position: 1
  required type: Stream
  but expression 's' is of type: Stream
proc readLine(s: Stream; line: var TaintedString): bool
  first type mismatch at position: 1
  required type: Stream
  but expression 's' is of type: Stream

expression: readLine(s, l)
  while s.readLine(l):