Print the program version.

def print_version(self):
        """
        Print the program version.
        """

        if not self._version:
            return self

        if not self._title:
            print('  %s %s' % (self._name, self._version))
            return self

        print('  %s (%s %s)' % (self._title, self._name, self._version))
        return self