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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 _unmount_devicemapper(self, cid):
 """ Devicemapper unmount backend. """

        mountpoint = self.mountpoint
        Mount.unmount_path(mountpoint)

        cinfo = self.client.inspect_container(cid)
        dev_name = cinfo['GraphDriver']['Data']['DeviceName']

        Mount.remove_thin_device(dev_name)
        self._cleanup_container(cinfo)