Output array is read-only

[dineshbvadhia]

In the tests, performing an operation on the array test_fastnumpyio_save after it has been loaded gives an output array is read-only error:

start = timer()
for i in range(iterations):
    buffer = io.BytesIO(fastnumpyio_save_data)
    test_fastnumpyio_save=load(buffer)
print("fastnumpyio.load:",timedelta(seconds=timer()-start))

test_fastnumpyio_save *= 4.1
ValueError: output array is read-only

Why does it load a read-only array? Secondly, what is the best option to make the array mutable without incurring a performance penalty?