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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 drive_rotational_speed_rpm(self):
 """Gets the set of rotational speed of the HDD drives"""

        drv_rot_speed_rpm = set()
        for member in self.get_members():
            if member.rotational_speed_rpm is not None:
                drv_rot_speed_rpm.add(member.rotational_speed_rpm)
        return drv_rot_speed_rpm