[Discuss-gnuradio] flags / xml to supress Add throttle warning ?

I've built an OOT for some physical SDR hardware.

However, when compiling a flowgraph in gnruradio-companion

it prints a warning message about no audio or rf sink, so please

insert a throttle.

Since my module actually paces the samples in hardware, I don't

want a throttle.  How can I supress the warning message?

Looking through some GRC blocks, I've found two tags:

<throttle>1</throttle>

and another is

<flags>throttle</flags>

Reading the documentation that discusses XML tags in the block,
http://gnuradio.org/redmine/projects/gnuradio/wiki/GNURadioCompanion#Creating-the-XML-Block-Definition

it doesn't mention these tags, or what they do. Is one of these the

correct way to suppress the flowgraph compile warning?

-- Tom, N5EG