Returns true if the supplied unpickler matches the type tag in the SerializedValue.
Returns true if the supplied unpickler matches the type tag in the SerializedValue. This can return false in some cases where parse[T] could succeed (parse is allowed to use duck typing). So this should only be used when the type to be unpickled is not known for sure and a discriminator is required. The advantages of hasTag over simply attempting to parse are that it doesn't throw an expensive exception on match failure, and it can't accidentally match a structurally-compatible but distinct type.
We serialize to and from this opaque type. The idea is to hide exactly what we can serialize from/to and hide which library we use to do it.
What this will expose is the mechanism of using Pickler/Unpickler to handle unknown serialized values.