message: Expand docstring of GraphTypeTopologyView
diff: @@ -377,6 +377,9 @@ struct NodeTypeIdEdge {
  // This is just like GraphTopologyView but with (NodeDef, TypeAttrId) pairs as
  // the vertices instead of just NodeDef.
  +// For example, if node A has output A:0 with TypeAttrId 'T', and node B has
  +// input B:0 with TypeAttrId 'U', and input B:0 connects to output A:0, there
  +// will be an edge from (A, T) to (B, U).
  class GraphTypeTopologyView {
  public:
  GraphTypeTopologyView() = default;
  