docs: def get_instance_type(self, port):
          """Determine the port type based on device owner and vnic type"""
          if port[portbindings.VNIC_TYPE] == portbindings.VNIC_BAREMETAL:
              return a_const.BAREMETAL_RESOURCE
          owner_to_type = {
              n_const.DEVICE_OWNER_DHCP: a_const.DHCP_RESOURCE,
              n_const.DEVICE_OWNER_DVR_INTERFACE: a_const.ROUTER_RESOURCE,
              trunk_consts.TRUNK_SUBPORT_OWNER: a_const.VM_RESOURCE}
          if port['device_owner'] in owner_to_type.keys():
              return owner_to_type[port['device_owner']]
          elif port['device_owner'].startswith(
                  n_const.DEVICE_OWNER_COMPUTE_PREFIX):
              return a_const.VM_RESOURCE
          return None