code: def height(self):
          
          if self.__children_:
              return max([child.height for child in self.__children_]) + 1
          else:
              return 0
docs: Number of edges on the longest path to a leaf `Node`.
  
          >>> from anytree import Node
          >>> udo = Node("Udo")
          >>> marc = Node("Marc", parent=udo)
          >>> lian = Node("Lian", parent=marc)
          >>> udo.height
          2
          >>> marc.height
          1
          >>> lian.height
          0