I am working on an OSM project in which we have a requirement of customizing Initiate Billing and Fulfill Billing requests. Now in previous PIP (O2A for OSM v7.0.3) the cartridges were not sealed and hence it was pretty simple to customize it. Now Oracle must be having a good reason to seal the billing cartridge with regards to consideration towards extensibility. However there is no clear documentation. O2A for OSM v2.0.1 guide does mention that existing functions inside sealed cartridges can be extended but there is no documentation on how to do it. They have only covered all the entities that need to be created from scratch.
We need a solution as it is pretty import for design decision and on basis of this only we can proceed ahead. Otherwise there will be no option left but to unseal it and do customization as we used to do earlier.