A scripting API for Blender's Geometry Nodes:

from geometry_script import *

@tree("Repeat Grid")
def repeat_grid(geometry: Geometry, width: Int, height: Int):
    g = grid(
        size_x=width, size_y=height,
        vertices_x=width, vertices_y=height
    ).mesh.mesh_to_points()
    return g.instance_on_points(instance=geometry)

1. Download the source code
2. Open Blender > Preferences > Add-ons
3. Choose Install... and select the downloaded ZIP file

Or you can get it from the Blender Market.

Geometry Script is a robust yet easy to use Python API for creating Geometry Nodes with code.

At a certain point, Geometry Node trees become unmanagably large. Creating node trees in Python enables quicker editing and reorganization of large, complex trees.

Geometry Script has all of the performance and capabilities of Geometry Nodes, but in a more managable format. The scripts are converted directly to Geometry Node trees making them easy to tweak for others unfamiliar with scripting.

Read the documentation for more information on installation, syntax, and tutorials.