[https://github.com/python-control/python-control/blob/a11d3befaba596991da1cf9a0c568a01c9b073e2/control/nlsys.py#L555](In nlsys.py) the call to .linearize() goes through a finite forward difference process to compute the state space matrices. We prefer to use central difference in some analysis cases, and I've gone about hard-coding the linearize function to calculate the central difference.

Has the central difference been implemented somewhere else? Would this be a useful addition to be able to select between the current forward difference and the central difference via an extra keyword argument?