You're seeing just the function call, go back to AMQPHelpers.RPC module for more information.
Link to this function

call(adapter \\ Adapter, connection, exchange, routing_key, payload, options \\ [])


Executes a remote procedure call.

This function sends the given messages and waits for a response using Direct Reply-to.

This function uses a Task internally to wait for responses. This means all the caveats and OTP compatibility Task issues apply here too. Check call_nolink/7 for more information.