Insantiates the subparsers for all commands

def subparsers(self):
        """
        Insantiates the subparsers for all commands
        """
        if self._subparsers is None:
            apkw = {
                'title': 'commands',
                'description': 'Commands for the %s program' % self.parser.prog,
            }
            self._subparsers = self.parser.add_subparsers(**apkw)
        return self._subparsers