We use the Python 3.x style
imports from the
__future__ module must be done
before any other executable statement.
# - - - - - I m p o r t s from __future__ import print_function
First we'll need to import the standard Python
sys module, which will give us access to the
command line arguments and the standard I/O streams.
Command line argument processing is done with the standard
argparse module; see its Python library
To read the RNG schema file, we need the
lxml.etree module, which we call
import lxml.etree as et