This seems to be part of Mojang's [DataFixerUpper](https://github.com/Mojang/DataFixerUpper) library. The source for the `Codec` interface can be found at [`src/main/java/com/mojang/serialization/Codec.java`](https://github.com/Mojang/DataFixerUpper/blob/e843dac1eb96af7b86b1e11165afeca7caffb7e6/src/main/java/com/mojang/serialization/Codec.java#L34).

I used MCP-Reborn to view the source code of Minecraft. But I can't seem to find the class named "Codec". I can see it referenced in the code, but not the code that makes the class. Anyone know where I can find the code for that class?

com.mojang.serialization.Codec