How to use the stestr.commands function in stestr

def run(self):
        table = [('command', 'description')]
        for command in stestr.commands.iter_commands():
            table.append((command.name, command.get_summary()))
        self.ui.output_table(table)

def _parse_one(self, arg):
        try:
            return commands._find_command(arg)
        except KeyError:
            raise CustomError("Could not find command '%s'." % arg)

# Licensed under either the Apache License, Version 2.0 or the BSD 3-clause
# license at the users choice. A copy of both licenses are available in the
# project source as Apache-2.0 and BSD. You may not use this file except in
# compliance with one of these two licences.
# 
# Unless required by applicable law or agreed to in writing, software
# distributed under these licenses is distributed on an "AS IS" BASIS, WITHOUT
# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
# license you chose for the specific language governing permissions and
# limitations under that license.

"""List available commands."""

import stestr.commands

class commands(stestr.commands.Command):
    """List available commands."""

    def run(self):
        table = [('command', 'description')]
        for command in stestr.commands.iter_commands():
            table.append((command.name, command.get_summary()))
        self.ui.output_table(table)