code: def partition(arr, first, last):
      wall = first
      for pos in range(first, last):
          if arr[pos] < arr[last]:  # last is the pivot
              arr[pos], arr[wall] = arr[wall], arr[pos]
              wall += 1
      arr[wall], arr[last] = arr[last], arr[wall]
      return wall
  
label_desc: Use image node_id 3 for calling a global function with example usage: partition(arr, first, last) and returns: wall