At the very bottom of the existing document I added the clean_ss() function, adjusting it slightly to confirm with the existing imports in the document. Re-wrote the documentation to have the same style as the rest of the document

Added the clean_tf() function at the bottom of xferfcn.py, adjusting it slightly to be conform with the existing imports in the file and adding one import from another file of the control library. Also adjusted the documentation for the function to match the existing style. Additionally fixed a formatting error in the documentation for clean_ss()

Added the fival() function at the bottom of thetimeresp.py file, slightly adjusting it to conform with the existing imports in the file and adding a couple of new import statements. Adjusted the documentation so that its format is conform with the rest of the file. Slightly adjusted the format of the documentation for clean_tf() in the xferfcn.py file

…unction and StateSpace classes

While the functions clean_ss and clean_tf remain as separate functions in the respective files, the function clean() has been added in the respective form to the TransferFunction ans StateSpace classes. This makes it possible to still go directly from a StateSpace to a clean TransferFunction (or vice versa) but makes it easier to clean either one of the two if it is already in the desired form. The fival function remains as a function in the timeresp.py file, but by importing it to the other two files and including it in the aforementioned classes it is now possible to, for instance, use sys.fival(**) where sys is a StateSpace or TransferFunction.

Used the property that .clean() is now a function of the TransferFunction class to simplify the code for the clean_tf() function, which performs the same task but opens up the input to not just TrasnferFunction objects but also StateSpace objects.

The three files statesp.py, timeresp.py, and xferfcn.py all imported each other in a cyclical manner. I solved this issue by moving the import statements from the global positions at the top of said files to within the respective functions. Additionally I temporarily added a file to test the implementation of the functions using examples.

The clean_tf function was not making use of the input, output, and precision values passed to it. Fixed this issue. Also extended the documentation to include that the fival function returns None if an unstable system is checked for stability

Edited the fival stability check function such that the error message grammatically  accounts for one or multiple poles in the right half of the compley plane

The most recent version of tester.py contains information that, while going to be deleted at some point, is as of now still useful