Yield all Command objects represented by the python module.

    Module commands consist of a docopt-style module docstring and a callable
    Command class.

    Args:
        module: An ast.Module object used to retrieve docopt-style commands.

    Yields:
        Command objects that represent entry points to append to setup.py.

def _get_module_commands(module):
    # type: (ast.Module) -> typing.Generator[_EntryPoint, None, None]
    """Yield all Command objects represented by the python module.

    Module commands consist of a docopt-style module docstring and a callable
    Command class.

    Args:
        module: An ast.Module object used to retrieve docopt-style commands.

    Yields:
        Command objects that represent entry points to append to setup.py.
    """
    cls = next((n for n in module.body
                if isinstance(n, ast.ClassDef) and n.name == 'Command'), None)
    if not cls:
        return
    methods = (n.name for n in cls.body if isinstance(n, ast.FunctionDef))
    if '__call__' not in methods:
        return
    docstring = ast.get_docstring(module)
    for commands, _ in usage.parse_commands(docstring):
        yield _EntryPoint(commands[0], next(iter(commands[1:]), None), None)