array(3) {
  [1]=>
  array(2) {
    [0]=>
    int(3991)
    [1]=>
    int(4302)
  }
  [9]=>
  array(1) {
    [0]=>
    int(4260)
  }
  [21]=>
  array(1) {
    [0]=>
    int(9638)
  }
}