print by insert order

[ChestnutHeng]

root = pptree.Node("0")
n1 = pptree.Node("1", root)
n2 = pptree.Node("2", root)
n3 = pptree.Node("3", root)
should be print as:
0
┌────┴─────┬
1 2 3
not be:
0
┌────┴─────┬
1 3 2