code: def shrank(self, block=None, percent_diff=0, abs_diff=1):
          
          if block is None:
              block = self.block
          cur_nets = len(block.logic)
          net_goal = self.prev_nets * (1 - percent_diff) - abs_diff
          less_nets = (cur_nets <= net_goal)
          self.prev_nets = cur_nets
          return less_nets
docs: Returns whether a block has less nets than before
  
          :param Block block: block to check (if changed)
          :param Number percent_diff: percentage difference threshold
          :param int abs_diff: absolute difference threshold
          :return: boolean
  
          This function checks whether the change in the number of
          nets is greater than the percentage and absolute difference
          thresholds.