def METHOD_NAME(document, comm):
    div1 = Div()
    div2 = Div()
    gspec = GridSpec(width=900, height=500)
    gspec[0, 0:2] = div1
    gspec[1, 2] = div2
    model = gspec.get_root(document, comm=comm)
    assert model.children == [(div1, 0, 0, 1, 2), (div2, 1, 2, 1, 1)]
    assert div1.width == 600
    assert div1.height == 250
    assert div2.width == 300
    assert div2.height == 250