code: def _missing_(cls, value):
          
          if not (isinstance(value, int) and 0 <= value <= 65535):
              raise ValueError('%r is not a valid %s' % (value, cls.__name__))
          if 2 <= value <= 6:
              extend_enum(cls, 'Unassigned [%d]' % value, value)
              return cls(value)
          if 8 <= value <= 13:
              extend_enum(cls, 'Unassigned [%d]' % value, value)
              return cls(value)
          if 21 <= value <= 23:
              extend_enum(cls, 'Unassigned [%d]' % value, value)
              return cls(value)
          if 29 <= value <= 31:
              extend_enum(cls, 'Unassigned [%d]' % value, value)
              return cls(value)
          if 33 <= value <= 39:
              extend_enum(cls, 'Unassigned [%d]' % value, value)
              return cls(value)
          if 52 <= value <= 59:
              extend_enum(cls, 'Unassigned [%d]' % value, value)
              return cls(value)
          if 63 <= value <= 69:
              extend_enum(cls, 'Unassigned [%d]' % value, value)
              return cls(value)
          if 71 <= value <= 89:
              extend_enum(cls, 'Unassigned [%d]' % value, value)
              return cls(value)
          if 91 <= value <= 99:
              extend_enum(cls, 'Unassigned [%d]' % value, value)
              return cls(value)
          if 101 <= value <= 8191:
              extend_enum(cls, 'Unassigned [%d]' % value, value)
              return cls(value)
          if 8192 <= value <= 16383:
              # [RFC 7401]
              extend_enum(cls, 'Reserved for Private Use [%d]' % value, value)
              return cls(value)
          if 16385 <= value <= 40959:
              extend_enum(cls, 'Unassigned [%d]' % value, value)
              return cls(value)
          if 40960 <= value <= 65535:
              # [RFC 7401]
              extend_enum(cls, 'Reserved for Private Use [%d]' % value, value)
              return cls(value)
          super()._missing_(value)
docs: Lookup function used when value is not found.