What is the lldb summary string for SIMD types?

I apologize if this isn't the correct forum. I have written a custom type that conforms to the SIMD protocol. At the lldb prompt I can type (lldb) print(shape) and the value of the type's description property is displayed.
However, I would like the value in the local variables window to display the summary value so I don't have to print it every time. The Swift.SIMD generic types show a summary string value, but I can't figure out how to define one for my type. The SIMD storage is opaque.
I would really appreciate it if someone could let me know what the summary string is for the SIMD types, as I imagine what I need is very similar.

Thank you, Ed