I am trying to understand T-Joins, and I am struggling with the definition.
This is the working definition that I am using (from my lecture course)
G is an undirected graph. T is a subset of the vertices. A subset of edges J is called a T-Join if T equals the set of odd-degree vertices in the subgraph G' of G with V(G') = V(G), and E(G') = J.
Here is an example that I have made for myself
A graph G
I then (somehow?) select some vertices (a set named T in the definition) circled in red
I then choose the edges which ensure that all elements of T have odd-degree. These edges are named J in the definition, and are shown with red lines in the image
So the T-Join itself is shown with the squiggly red lines.
Is this a correct example?
How do I select the elements of T? Is there only one set J to satisfy a given set T of a graph G?
Thank you for your time and help