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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:

def _list_iter(host=None, path=None):
    '''
    Return a generator iterating over hosts

    path
        path to the container parent
        default: /var/lib/lxc (system default)

        .. versionadded:: 2015.8.0
    '''
    tgt = host or '*'
    client = salt.client.get_local_client(__opts__['conf_file'])
    for container_info in client.cmd_iter(
        tgt, 'lxc.list', kwarg={'path': path}
    ):
        if not container_info:
            continue
        if not isinstance(container_info, dict):
            continue
        chunk = {}
        id_ = next(six.iterkeys(container_info))
        if host and host != id_:
            continue
        if not isinstance(container_info[id_], dict):
            continue
        if 'ret' not in container_info[id_]:
            continue
        if not isinstance(container_info[id_]['ret'], dict):
            continue
        chunk[id_] = container_info[id_]['ret']
        yield chunk