How does "Bundle Constructor" work and where can I find documentation on its use?

I’m trying to build bundles, which I currently believe are how one handles collections of attributes which are defined at runtime.

The documentation for “Bundle Constructor” makes some vague references to a “dynamic input attribute” but I can’t find any reference or mention of this anywhere else. How are these things supposed to be used?

Is there any documentation on them? Examples?

I want to be able to construct an arbitrary collection of attributes coming off the network from my custom node, and then expose them as a bundle output which i can query at run time to extract the value of expected attributes.