def _create_model_request(name, role, container_def=None, tags=None):
    """Placeholder docstring"""
    request = {'ModelName': name, 'ExecutionRoleArn': role}
    if isinstance(container_def, list):
        request['Containers'] = container_def
    else:
        request['PrimaryContainer'] = container_def
    if tags:
        request['Tags'] = tags
    return request
