code: def is_jump_back(self, offset, extended_arg):
          
          if self.code[offset] != self.opc.JUMP_ABSOLUTE:
              return False
          return offset > self.get_target(offset, extended_arg)
docs: Return True if the code at offset is some sort of jump back.
          That is, it is ether "JUMP_FORWARD" or an absolute jump that
          goes forward.