Can provider support multi serialization protocols?

I'm trying to change my service's serialization protocol gracefully, so I want to implement a feature like this:

provider can support multi serialization protocols, and consumer assigns its serialization protocol, provider can receive consumer's request correctlly if consumer's serialization protocol is supported by provider.

I found there's a issue #4640 related my problem, and known that the consumer can't assign self serizalization protocol.

I try to set the `dubbo.protocol.serialization = protostuff,fastjson` in the `application.yml`, the provider service can start up successfully and the registry url contains `serialization` field, but when I send request to the provider, I got an exception `No such extension org.apache.dubbo.common.serialize.Serialization by name protostuff,fastjson`, it seems provider can't support multi serialization protocols, but why the [code](https://github.com/apache/dubbo/blob/master/dubbo-config/dubbo-config-api/src/main/java/org/apache/dubbo/config/ProtocolConfig.java#L339) shows it seems it supports?

Am I using it wrong?

And more, I think it's not graceful enough that consumer can't assign self serialization protocol, can you introduce to me why design it like this?