confiction with "ss" function provided by the control system toolbox

[shaopengyuan]

When I use the function "ss" to create linear state space model after directory ParNMPC with the subfolders included into matlab path, the following error arised:
错误使用 ss
如果类定义了超类，则所有超类必须均为句柄类，或者所有超类均不为句柄类。
In English, which means when the class defined with superclass, then all of the superclasses must be handle class ,or none of them is handle class.

After excluded ParNMPC, the error disappeared.

So, I think the function "ss" maybe conflict with ParNMPC. I have searched the ParNMPC for the keyword "ss", but no result found.
@ideaDeng would you like to find which lines introudce this confliction and fix it.