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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def shrank(self, block=None, percent_diff=0, abs_diff=1):
 """ 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. """

        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