in crumb-compiler/src/main/kotlin/com/uber/crumb/internal/wire/Message.kt [107:115]
fun addUnknownField(
tag: Int,
fieldEncoding: FieldEncoding,
value: Any?
): Builder<M, B> = apply {
prepareForNewUnknownFields()
val protoAdapter = fieldEncoding.rawProtoAdapter() as ProtoAdapter<Any>
protoAdapter.encodeWithTag(unknownFieldsWriter!!, tag, value)
}