Hi,
Something weird, if anyone can give some hint.
Expected outputs:
Cost at initial w and b (zeros): 0.693
Cost at test w and b (nonzeros): 0.218 /test_w = np.array([0.2, 0.2]), test_b = 24/
What I’m getting is…

wrong cost at initial w and b (zeros): 0.007.
wrong cost at test w and b (nonzeros): 0.000
Error message:
"AssertionError: Wrong output. Expected: 2.15510667 got: 0.15761825329865956 "
…I guess these relate to one of the intermediary results. 
tweak my code at the last line, removing the “… / m” part of the expression
right cost at initial w and b (zeros): 0.693.
wrong cost at test w and b (nonzeros): 0.000
Error message:
" AssertionError: Wrong output. Expected: 2.15510667 got: 0.7880912664932977
"
…I guess these relate to the same intermediary results.