comefrom: <qiyuangong>024_Swap_Nodes_in_Pairs_1.py
code: def swapPairs( head):
      current = last = last2 = head
      while current is not None:
          nex = current.next
          if current == last.next:
              last.next = nex
              current.next = last
              if last == head:
                  head = current
              else:
                  last2.next = current
              last2 = last
              last = nex
          current = nex
      return head
masked: def sample_funcname ( var_0 ) :
      var_3 = var_1 = var_2 = var_0
      while var_3 is not None :
          var_6 = var_3.next
          if var_3 == var_1.next :
              var_1.next = var_6
              var_3.next = var_1
              if var_1 == var_0 :
                  var_0 = var_3
              else :
                  var_2.next = var_3
              var_2 = var_1
              var_1 = var_6
          var_3 = var_6
      return var_0
  