def _is_plugable_7port_usb3_part3_hub(node):
  """Check if a node is the "USB3 branch" of
  a Plugable 7-Port USB-3 Hub (Model USB3-HUB7BC)
  The topology of this device is a 4-port hub,
  with another 4-port hub connected on port 1.
  """
  if '2109:8110' not in node.desc:
    return False
  if not node.HasPort(1):
    return False
  return '2109:8110' in node.PortToDevice(1).desc