How to publish a proto type when the base parent class doesn't use ISAAC_PROTO_TX

the RosToProtoConverter.hpp script has a base class that can be used to parse any kind of ros message and publishes as a proto. But the RosToProto() class doesn’t use ISAAC_PROTO_TX( ) to create a TX, instead it directly uses
alice::ProtoTx<IsaacProtoType>& tx_proto() { return tx_proto_; }
alice::ProtoTx<IsaacProtoType> tx_proto_{this, "proto"};

So, when I try to fill the ToProto( data, tx_proto.initProto(), tx_proto.buffers( ) ), I am not sure how to create an instance of the prototype. (by defauly we use msg = tx_data().initProto() and updating the proto is not applicable here).