types derived from built-in types (i.e. str, int, float) do not serialize correctly

[keotl]

In this example, serializing the Player class yields an incorrect response.

@Serializable
class Player(object):
    player_id: PlayerIdentifier

class PlayerIdentifier(str):
    pass

Actual

{
    "player": {}
}

Expected

{
    "player": "my_player_id"
}