docs: def decap(self, orig_pkt):
          """decapsulate a MACsec frame"""
          if orig_pkt.name != Ether().name or orig_pkt.payload.name != MACsec().name:  # noqa: E501
              raise TypeError('cannot decapsulate MACsec packet, must be Ethernet/MACsec')  # noqa: E501
          packet = copy.deepcopy(orig_pkt)
          prev_layer = packet[MACsec].underlayer
          prev_layer.type = packet[MACsec].type
          next_layer = packet[MACsec].payload
          del prev_layer.payload
          if prev_layer.name == Ether().name:
              return Ether(raw(prev_layer / next_layer))
          return prev_layer / next_layer