code: def build_D3treepie(old, MAX_DEPTH, level=1, toplayer=None):
      
      d = {}
      if not old:
          old = toplayer
      for x in old:
          label = x.bestLabel(quotes=False).replace("_", " ")
          if x.children() and level < MAX_DEPTH:
              size = len(x.children())
              d[x.qname] = [
                  label, [size, size],
                  build_D3treepie(x.children(), MAX_DEPTH, level + 1)
              ]
          else:
              size = 1
              d[x.qname] = [label, [size, size], {}]
  
      return d
docs: Create the JSON needed by the treePie viz
  	http://bl.ocks.org/adewes/4710330/94a7c0aeb6f09d681dbfdd0e5150578e4935c6ae
  
  	Eg
  
  	['origin' , [n1, n2],
  			{ 'name1' :
  				['name1', [n1, n2],
  					{'name1-1' : ...}
  				] ,
  			} ,
  	]