code: def parse_tree(self, tree_node, validate):
          
          self.info = collect_info(self.filename)
          self.source_ids = collections.defaultdict(list)
          t0 = time.time()
          for depth, branchinglevel_node in enumerate(tree_node.nodes):
              self.parse_branchinglevel(branchinglevel_node, depth, validate)
          dt = time.time() - t0
          if validate:
              bname = os.path.basename(self.filename)
              logging.info('Validated %s in %.2f seconds', bname, dt)
docs: Parse the whole tree and point ``root_branchset`` attribute
          to the tree's root.