code: protected P upConvertPayload(GenericRecord inputRecord) throws DataConversionException {
      try {
        Schema payloadSchema = getPayloadSchema(inputRecord);
        // Set writer schema
        latestPayloadReader.setSchema(payloadSchema);
  
        byte[] payloadBytes = getPayloadBytes(inputRecord);
        Decoder decoder = DecoderFactory.get().binaryDecoder(payloadBytes, null);
  
        // 'latestPayloadReader.read' will convert the record from 'payloadSchema' to the latest payload schema
        return latestPayloadReader.read(null, decoder);
      } catch (Exception e) {
        throw new DataConversionException(e);
      }
    }
docs: Convert the payload in the input record to a deserialized object with the latest schema
  
  @param inputRecord the input record
  @return the schema'ed payload object