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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 block_perms(self):
 """If the circuit is reducible into permutations within subranges of the full range of channels, this yields a tuple with the internal permutations for each such block. :type: tuple """

        if not self._block_perms:
            self._block_perms = permutation_to_block_permutations(
                self.permutation)
        return self._block_perms