code: public <M extends net.morimekta.providence.PMessage<M, F>, F extends net.morimekta.providence.descriptor.PField>
      M unwrapMessage(@javax.annotation.Nonnull net.morimekta.providence.descriptor.PMessageDescriptor<M,F> descriptor) {
          return unwrapMessage(descriptor, new net.morimekta.providence.serializer.DefaultSerializerProvider());
      }
docs: Unwrap a message from this wrapper message. This will use the default
  serializer provider to find a suitable serializer to use to deserialize
  the wrapped message. If no serializer is available, or the message
  cannot be deserialized an unchecked IO exception is thrown.
  
  @param descriptor The message type to unpack from the content.
  @param <M> The message type
  @param <F> The message field type
  @return The unwrapped message.