void insertion_sort(struct darray* arr){
  printf("Entered Sort\n");
  int i;
  int k;
  int j;
  for (int i = 0; i <= arr->size - 1; i++)
  {
    k = arr->cells[i];
    j = i - 1;
    while(j >= 0 && arr->cells[j] > k)
    {
      arr->cells[j+1] = arr->cells[j];
      j = j - 1;
    }
    arr->cells[j+1] = k;
 }
 printf("completed sort\n");
}