code: def __get_delta_files(self):
          
          files = [(d, f) for d in self.dirs for f in listdir(d) if isfile(join(d, f))]
  
          deltas = OrderedDict()
          for d, f in files:
              file_ = join(d, f)
  
              if not Delta.is_valid_delta_name(file_):
                  continue
  
              delta = Delta(file_)
  
              if d not in deltas:
                  deltas[d] = []
              deltas[d].append(delta)
  
          # sort delta objects in each bucket
          for d in deltas:
              deltas[d].sort(key=lambda x: (x.get_version(), x.get_priority(), x.get_name()))
  
          return deltas
docs: Search for delta files and return a dict of Delta objects, keyed by directory names.