For senses to be treated like entities, the "lexeme-sense" entity type must be defined in an entitytypes file, similar to wikibase.entitytpes.php, as described in T165328:

• define serializer/deserializer (immediately!)
  • the deserializer may also be hardwired in the parent's deserializer. But we will need to be able to serialize Sense standalone, without their parent, for API responses etc.
• define EntityRdfBuilder (eventually)
• define ChangeOp deserializers
• TBD: define the view factory here, or hard code it in the parent's view.

However, do NOT defined a content model or EntityHandler!