How to test numpy arrays that are not only numeric for almost equality?

import numpy as np

a = np.array([1/3, 2, None])
a
Out[11]: array([0.3333333333333333, 2, None], dtype=object)
b = np.array(a)
b
Out[13]: array([0.3333333333333333, 2, None], dtype=object)
np.testing.assert_almost_equal(a, b)

outputs

Traceback (most recent call last):   File "C:\code\EPMD\Kodex\EPD_Prerequisite\python_3.7.6\lib\site-packages\IPython\core\interactiveshell.py", line 3319, in run_code
    exec(code_obj, self.user_global_ns, self.user_ns)   File "<ipython-input-14-f86262d61654>", line 1, in <module>
    np.testing.assert_almost_equal(a, b)   File "C:\code\EPMD\Kodex\EPD_Prerequisite\python_3.7.6\lib\site-packages\numpy\testing\_private\utils.py", line 585, in assert_almost_equal
    return assert_array_almost_equal(actual, desired, decimal, err_msg)   File "C:\code\EPMD\Kodex\EPD_Prerequisite\python_3.7.6\lib\site-packages\numpy\testing\_private\utils.py", line 1047, in assert_array_almost_equal
    precision=decimal)   File "C:\code\EPMD\Kodex\EPD_Prerequisite\python_3.7.6\lib\site-packages\numpy\testing\_private\utils.py", line 794, in assert_array_compare
    val = comparison(x, y)   File "C:\code\EPMD\Kodex\EPD_Prerequisite\python_3.7.6\lib\site-packages\numpy\testing\_private\utils.py", line 1038, in compare
    z = abs(x - y) TypeError: unsupported operand type(s) for -: 'NoneType' and 'NoneType'

How do I avoid for loops here?