def activate(client, name, file_=None):
    """Activate a model view.

    Args:
        client (obj):
            creopyson Client.
        name (str):
            View name.
        `file_` (str, optional):
            Model name. Defaults is current active model.

    Returns:
        None

    """
    data = {'name': name}
    if file_ is not None:
        data['file'] = file_
    else:
        active_file = client.file_get_active()
        if active_file is not None:
            data['file'] = active_file['file']
    return client._creoson_post('view', 'activate', data)
