using D3Trees
children = [[2,3], [], [4], []]
text = ["one\n(second line)", "2", "III", "four"]
style = ["", "fill:red", "r:14", "opacity:0.7"]
link_style = ["", "stroke:blue", "", "stroke-width:10px"]
tooltip = ["pops", "up", "on", "hover"]
t = D3Tree(children,
text=text,
style=style,
tooltip=tooltip,
link_style=link_style)