Adding/subtracting 2 Waveform objects does not output a Waveform object as expected

See example:

import numpy as np
from madarrays import Waveform

n = 10
x = Waveform(np.zeros(n))
y = Waveform(np.ones(n))
a = x + y
s = x - y
print(type(x), type(y))
print(type(a), type(s))

<class 'madarrays.waveform.Waveform'> <class 'madarrays.waveform.Waveform'>

<class 'madarrays.mad_array.MadArray'> <class 'madarrays.mad_array.MadArray'>