import klayout.db as kdb
layout = kdb.Layout()
layer1 = layout.layer(kdb.LayerInfo('1/0'))
TOP = layout.create_cell("TOP")
box = kdb.DBox(kdb.DPoint(-4500, -4500), kdb.DPoint(4500, 4500))
TOP.shapes(layer1).insert(box)
layout.write('test.gds')