How do I bind a registered service to an entity?

1

I want to add a service to the cover component.But after registration, the service is not bound to the entity.`
def setup_platform(hass, config, add_devices, discovery_info=None):
“”“Set up the Demo covers.”""
coverItems = []
for device in hass.data[“covers”]:
coverItems.append(DemoCover(hass, device, device[‘posi’]))
add_devices(coverItems, True)

class DemoCover(CoverDevice):
“”“Representation of a demo cover.”""

# pylint: disable=no-self-use
def __init__(self, hass, device,name, position=None, tilt_position=None,
             device_class=None, supported_features=None):
    """Initialize the cover."""
    self.hass = hass
    self._name = name
    self.hass.services.register("cover","maintain_scene",self.maintain_scene)//register services
    self._position = position
    self._device_class = device_class
    self._supported_features = supported_features
    self._set_position = None
    # self._set_tilt_position = None
    #self._set_position = 0
    self._tilt_position = tilt_position
    self._requested_closing = True
    self._requested_closing_tilt = True
    self._unsub_listener_cover = None
    self._unsub_listener_cover_bar = None
    self._unsub_listener_cover_tilt = None
    self._is_opening = False
    self._is_closing = False
    self._deviceid = device.get('id')
    self._position_step = self.alltime(10) 
    self.transport = hass.data['transport']
    if position is None:
        self._closed = True
    else:
        self._closed = self.current_cover_position <= 0
    self.gethhznCoverPosition()
    `

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