Graph / subgraph attributes

I’d be happy to, if this was in a language that I could program in. Unfortunately…

As the author of this code, could you explain how graphviz uses attributes set on a graph element? I specifically mean in that part of the grammar:

attr_stmt : ( `graph` | `node` | `edge` ) attr_list

I understand node and edge, but I’m not sure what graph does.

I suppose I should have phrased my question that way from the beginning…