code: def remove(self):
          
          if self.parent:
              for i, node in enumerate(self.parent.children):
                  if node is self:
                      self.parent.changed()
                      del self.parent.children[i]
                      self.parent = None
                      return i
docs: Remove the node from the tree. Returns the position of the node in its
          parent's children before it was removed.