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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 make_id():
    ''' Return a new unique ID for a Bokeh object.

    Normally this function will return simple monotonically increasing integer
    IDs (as strings) for identifying Bokeh objects within a Document. However,
    if it is desirable to have globally unique for every object, this behavior
    can be overridden by setting the environment variable ``BOKEH_SIMPLE_IDS=no``.

    Returns:
        str

    '''
    global _simple_id

    if settings.simple_ids(True):
        with _simple_id_lock:
            _simple_id += 1
            return str(_simple_id)
    else:
        return make_globally_unique_id()