def METHOD_NAME():
    data = np.random.random((3, 3))
    # Build the following labels with an isolated seed
    # in the bottom-right corner:
    # array([[ 0.,  1., -1.],
    #        [-1., -1., -1.],
    #        [-1., -1.,  2.]])
    labels = -np.ones((3, 3))
    # Make a seed
    labels[0, 1] = 1
    # Point next to the seed
    labels[0, 0] = 0
    # Set a seed in the middle, it is surrounded by masked pixels
    labels[2, 2] = 2
    # The expected result is:
    # array([[ 1.,  1., -1.],
    #        [-1., -1., -1.],
    #        [-1., -1., -1.]])
    expected = np.array(
        [[1.0, 1.0, -1.0], [-1.0, -1.0, -1.0], [-1.0, -1.0, -1.0]]
    )
    np.testing.assert_array_equal(expected, _random_walker(data, labels))