old_contents: # Tai Sakuma <tai.sakuma@cern.ch>
  from Events import Events
  from BranchBuilder import BranchBuilder
  
  ##__________________________________________________________________||
  class BEvents(Events):
      def __init__(self, tree, maxEvents = -1, start = 0):
          super(BEvents, self).__init__(tree, maxEvents, start)
          tree.SetBranchStatus('*', 0)
          self.branches = { }
          self.buildBranch = BranchBuilder()
  
      def __repr__(self):
          return '{}({}, branches = {!r})'.format(
              self.__class__.__name__,
              super(BEvents, self)._repr_contents(),
              self.branches
          )
  
      def __getattr__(self, name):
          if name in self.branches: return self.branches[name]
          branch = self.buildBranch(self.tree, name)
          if branch is None: raise AttributeError("'" + str(self) + "' has no attribute '" + name + "'")
          self.branches[name] = branch
          if self.iEvent >= 0: self.tree.GetEntry(self.start + self.iEvent)
          return self.branches[name]
  
  ##__________________________________________________________________||
  
new_contents: # Tai Sakuma <tai.sakuma@cern.ch>
  from Events import Events
  from BranchBuilder import BranchBuilder
  
  ##__________________________________________________________________||
  class BEvents(Events):
      def __init__(self, tree, maxEvents = -1, start = 0):
          super(BEvents, self).__init__(tree, maxEvents, start)
          tree.SetBranchStatus('*', 0)
          self.branches = { }
          self.buildBranch = BranchBuilder()
  
      def __repr__(self):
          return '{}({}, branches = {!r})'.format(
              self.__class__.__name__,
              super(BEvents, self)._repr_contents(),
              self.branches
          )
  
      def __getattr__(self, name):
  
          if name in self.branches:
              return self.branches[name]
  
          branch = self.buildBranch(self.tree, name)
  
          if branch is None:
              raise AttributeError('{!r} has no attribute "{}"'.format(self, name))
  
          self.branches[name] = branch
  
          if self.iEvent >= 0:
              self.tree.GetEntry(self.start + self.iEvent)
  
          return self.branches[name]
  
  ##__________________________________________________________________||
  
subject: clean up the code