Because we use argparse.ArgumentParser to handle command-line flags we automatically get an error if the user omits the (mandatory) filename argument. Unfortunately this means that simply running psyclone -v to get the version number fails.
I think what needs to be done is check for a solitary -v flag before we call parse_args in the main() routine in the generator.py file.

• Order 2, first derivative operator
• Order 3, first derivative operator
• Order 4, first derivative operator
• Order 5, first derivative operator
• Order 6, first derivative operator
• Order 7, first derivative operator
• Order 8, first derivative operator
• Order 9, first derivative operator
• Order 2, second derivative operators
• Order 3, secon