convert
Converts a value this converter has claimed into something a codec can encode.
Nested values should go through SerializationContext.convert rather than being converted by hand, so that a failure deeper in the structure arrives with the path to it.
Return
A value some registered codec can encode.
Parameters
source
The value being sent.
expectedOid
The OID the server expects, or 0 when it is not yet known.
context
Access to the type manager and to nested conversion.