Function deserialize_custom_from_json 

pub fn deserialize_custom_from_json(
    type_name: &str,
    value: &Value,
) -> Result<Option<Data>, Error>

Looks up and runs the JSON deserializer for the given type name. Returns None if the type is not registered.

Errors

Returns an error if metadata contains the reserved identifier key, the payload is missing, or the deserializer fails.