This may be a little confusing, but a ‘Line’ is not the actual end result, it’s a geometry object that represents where the line will go. To actually draw the line you need to create a DetailCurve, which is the actual Detail Line.
Here’s the code that I’m talking about:
To run the code you’ll need to be in a transaction (or use Automatic transaction mode), and need to initialize the app and doc variables as you normally would. When you run the tool, the final result is this:
A simple line drawn on the page.