code: def _assemble_flowtable(self, values):
          
          values = map(lambda x: [] if x is None else x, values)
          src = values[0] + values[1]
          dst = values[2] + values[3]
  
          thistable = dict()
          for s in src:
              thistable[s] = dst
          return thistable
docs: generate a flowtable from a tuple of descriptors.