code: def child_count(self, path):
          
          stat = self.stat(path)
          if not stat:
              return 0
  
          count = stat.numChildren
          for _, _, stat in self.tree(path, 0, include_stat=True):
              if stat:
                  count += stat.numChildren
          return count
docs: returns the child count under path (deals with znodes going away as it's
          traversing the tree).