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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_block_devices(self):
 """Get list of processing block devices."""

        # Get the list and number of Tango PB devices
        tango_db = Database()
        pb_device_class = "ProcessingBlockDevice"
        pb_device_server_instance = "processing_block_ds/1"
        pb_devices = tango_db.get_device_name(pb_device_server_instance,
                                              pb_device_class)
        LOG.info('Number of PB devices in the pool = %d', len(pb_devices))

        pb_device_map = []
        for pb_device_name in pb_devices:
            device = DeviceProxy(pb_device_name)
            if device.pb_id:
                LOG.info('%s %s', pb_device_name, device.pb_id)
                pb_device_map.append((pb_device_name, device.pb_id))

        return str(pb_device_map)