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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 processing_blocks(self):
 """Return list of PBs associated with the subarray. <http://www.esrf.eu/computing/cs/tango/pytango/v920/server_api/server.html#PyTango.server.pipe> """

        sbi_ids = Subarray(self.get_name()).sbi_ids
        pbs = []
        for sbi_id in sbi_ids:
            sbi = SchedulingBlockInstance(sbi_id)
            pbs.append(sbi.processing_block_ids)
        return 'PB', pbs