Hey Angela,
thanks for the bug report and thanks to @ronald.jaepel for the quick help!
I created a fix here that you can install following this guide.
By the way, the reason why the automatic concentration profile does not look exactly (or even closely) like your original profile is due to the fact that under the hood it tries to approximate the original profile using a spline which is not really suited for discontinuous profiles like yours, especially since it has so little data to work with.
If you use more data, e.g.
time = np.linspace(0, 10, 1001)
c = np.zeros((1001))
c[100:501] = np.linspace(0, 4, 401)
c[500:901] = np.linspace(4, 0, 401)
then, it looks much better:
In future, we might add some more functionality, but for now, this is what we’ve got.