Who's supporting who?

This is a wonderful Wysteria shrub outside the back of my sisters house. When they moved into the house 16 years ago they extended the back of the house, but it was limited because they wanted to keep this wysteria. They built a pergola to support it, winding the tendrils of the wysteria around the pergola supports. Now, 16 years later, the Wysteria is amazing, and has very much become entwined with the pergola. So much so it has actually caused this post to twist.