docs: def sanitize(self):
          '''
          Check and optionally fix properties
          '''
          # Let the parent do its stuff
          super(Protocol, self).sanitize()
  
          # Check if the next header is of the right type, and fix this header
          # if we know better (i.e. the payload is a ProtocolElement so we know
          # the header_type)
          if isinstance(self.payload, Protocol):
              self.next_header = self.payload.header_type