`sim.py` Checking isinstance of function, error checking a function

[khan-asfi-reza]

In sim.py Line:507
checking if func is function, will cause error as there is no valid keyword saved as function in python.
A valid solution would be

if callable(func):

[engineerjoe440]

This is an excellent example of where this project started from, and how it still has plenty of room to grow!

I agree, this is an item that really should be updated.

Long ago, in a University lab-room far, far away, I wrote this without knowing very much about the functions that Python had to support this sort of operation. In fact, it originally used a test like:

if str(type(func)) == "<type function>":

Looking back is "fun" but it also makes me cringe. We should fix this ASAP!