comefrom: <doocs>0366.Find Leaves of Binary Tree_1.py
code: def dfs(root, prev, t):
      if root is None:
          return
      if root.left is None and root.right is None:
          t.append(root.val)
          if prev.left == root:
              prev.left = None
          else:
              prev.right = None
      dfs(root.left, root, t)
      dfs(root.right, root, t)
masked: def sample_funcname ( var_1 , var_2 , var_3 ) :
      if var_1 is None :
          return
      if var_1.left is None and var_1.right is None :
          var_3.append ( var_1.val )
          if var_2.left == var_1 :
              var_2.left = None
          else :
              var_2.right = None
      var_0 ( var_1.left , var_1 , var_3 )
      var_0 ( var_1.right , var_1 , var_3 )
  