def METHOD_NAME(self, cur):
    cur.execute('SELECT * FROM global_cell')
    rows = cur.fetchall()
    assert len(rows) == 3
    x = [row["x"] for row in rows]
    y = [row["y"] for row in rows]
    z = [row["z"] for row in rows]
    return {'x': x, 'y': y, 'z': z}