Nested While-loop Box

Write a function nested_while_loop_box that returns a box like the one from the previous assignment (also shown below), but this time, using nested while loops. Example of box:

****
****
****
****
import unittest

EXPECTED_BOX = """
****
****
****
****
""".lstrip()


class BoxTestCase(unittest.TestCase):

    def test_nested_box(self):
        self.assertEqual(nested_while_loop_box(), EXPECTED_BOX)