def set_child(self, i, child):
        child.parent = self
        self.children[i].parent = None
        self.children[i] = child
        self.changed()
Equivalent to 'node.children[i] = child'. This method also sets the
dataset/ETHPy150Open ctxis/canape/CANAPE.Scripting/Lib/lib2to3/pytree.py/Node.set_child