Trouble creating Bode plots from concatenated SOSs

Created by: areeda

The notebook at https://git.ligo.org/joseph-areeda/FilterDesignPOC/blob/master/FilterWorkbench.ipynb demonstrates the problem. The Bode plot attempt is at the vry end

The rest of it defines various filters an concatenates them.

The error message is "ValueError: freqresp() requires a SISO (single input, single output) system."