code: def set_endianess(self, pkt):
          
          end = self.endianess_from(pkt)
          if isinstance(end, str) and end:
              if isinstance(self.fld, UUIDField):
                  self.fld.uuid_fmt = (UUIDField.FORMAT_LE if end == '<'
                                       else UUIDField.FORMAT_BE)
              else:
                  # fld.fmt should always start with a order specifier, cf field
                  # init
                  self.fld.fmt = end[0] + self.fld.fmt[1:]
docs: Add the endianness to the format