How to access individual objects in a Compound object?

We want to access individual letter in the text3D Compound, and we've found there is a function called siblings(self, shape: "Shape", kind: Shapes, level: int = 1). We wonder how to call the siblings function properly??//

```
import cadquery as cq
from cadquery.vis import show

text_string = "Hello, CadQuery!"
font = "Arial"
size = 10 # in millimeters
text3D = cq.Workplane("XZ").text(text_string, combine = True, font = font, fontsize = size, distance = 2).val()
```