You're seeing just the function publish, go back to AMQPHelpers.Reliability.Producer module for more information.
Link to this function

publish(server, exchange, routing_key, payload, opts, timeout \\ 5000)


Publish a message ensuring that the broker receives it.

Similar to AMQPHelpers.Adapter.publish/5 but ensures that the broker receives the message sent. Some message delivery options are enabled by default (mandatory and persistent) and message_id option is required to track the message state.