Hi, Matt! very useful and informative articles. Thank you veru much! Could you tell me how do I read content of a flowFile, transform it the way I like, and write the output to a new flowFile attribute (not back to the content)? I was trying to return transformation result from the callback but caught the error: None required for void return which is fairly expected behaviour - callback returns to the session.read function, but the latter does not return anything, I assume. So we get the flowFile itself and its content residing in different namespaces and I can't figure out how can I use content of the flowFile to place it into the attribute. Could you kindly help me, Matt? ... View more