code: def reverse_ll(ll):
      prev_node = None
  
      while ll is not None:
          # save the current node
          current = ll
          # go to the next node
          ll = ll.next
  
          # change the pointer of the current node to point to the previous node
          current.next = prev_node
          # save the current node for the next iteration
          prev_node = current
  
      return prev_node
  
imports: from ll_helpers import ListNode
  from ll_helpers import build_ll, print_ll
label_desc: Use image node_id 1 for calling a global function with example usage: reverse_ll(ll) and returns: prev_node