Unlike KeyLitParser.parsed, the behavior of serialize / deserialize is not changed.
Unlike KeyLitParser.parsed, the behavior of serialize / deserialize is not changed. Only the insertion path and acquisition path are changed when building the syntax tree.
("depth1" / "depth2").extend( "depth3".parsed(codec)(XXX.apply)(XXX.unapply) )
be equal
{ "depth1": { "depth2": { "depth3": "xxx" } } }
parsed type of codec.
internal codec.