code: def _max_diameter(tree):
      '''Find max diameter in tree
      '''
      return 2. * max(max(node.points[:, COLS.R]) for node in tree.ipreorder()f _max_diameter(tree):
      '''Find max diameter in tree
      '''
      return 2. * max(max(node.points[:, COLS.R]) for node in tree.ipreorder())
docs: Find max diameter in tree