def TNE_metric(bpmn_graph):
    """
    Returns the value of the TNE metric (Total Number of Events of the Model)
    for the BPMNDiagramGraph instance.

    :param bpmn_graph: an instance of BpmnDiagramGraph representing BPMN model.
    """

    events_counts = get_events_counts(bpmn_graph)

    return sum(
        [count for _, count in events_counts.items()]
    )