forest = {
let trees = [ubertree]
d3.range(ubertree.height-1).forEach(level => {
let prev = trees[trees.length-1]
let current = hierarchy({
name: '',
children: [].concat(...prev.data.children.map(c => c.children ? c.children : []))
})
current.value = ubertree.value
trees.push(current)
})
return trees
}