code: def vdp_vlan_change(self, vsw_cb_data, vdp_vlan, fail_reason):
          
          LOG.debug("In VDP VLAN change VLAN %s" % vdp_vlan)
          try:
              with self.ovs_vdp_lock:
                  self.vdp_vlan_change_internal(vsw_cb_data, vdp_vlan,
                                                fail_reason)
          except Exception as e:
              LOG.error("Exception in vdp_vlan_change %s" % str(e))
docs: Callback Function from VDP when provider VLAN changes.
  
          This will be called only during error cases when switch
          reloads or when compute reloads.