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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 get_physical_drives(self):
 """Get all the RAID physical drives on the Server. This method returns all the physical drives on the server by examining all the controllers. :returns: a list of PhysicalDrive objects. """

        physical_drives = []
        for controller in self.controllers:
            # First add unassigned physical drives.
            for physical_drive in controller.unassigned_physical_drives:
                physical_drives.append(physical_drive)
            # Now add physical drives part of RAID arrays.
            for array in controller.raid_arrays:
                for physical_drive in array.physical_drives:
                    physical_drives.append(physical_drive)

        return physical_drives