Wrap a callback function to execute without first obtaining the
    document lock.

    Args:
        func (callable) : The function to wrap

    Returns:
        callable : a function wrapped to execute without a |Document| lock.

    While inside an unlocked callback, it is completely *unsafe* to modify
    ``curdoc()``. The value of ``curdoc()`` inside the callback will be a
    specially wrapped version of |Document| that only allows safe operations,
    which are:

    * :func:`~bokeh.document.Document.add_next_tick_callback`
    * :func:`~bokeh.document.Document.remove_next_tick_callback`

    Only these may be used safely without taking the document lock. To make
    other changes to the document, you must add a next tick callback and make
    your changes to ``curdoc()`` from that second callback.

    Attempts to otherwise access or change the Document will result in an
    exception being raised.

def without_document_lock(func):
    ''' Wrap a callback function to execute without first obtaining the
    document lock.

    Args:
        func (callable) : The function to wrap

    Returns:
        callable : a function wrapped to execute without a |Document| lock.

    While inside an unlocked callback, it is completely *unsafe* to modify
    ``curdoc()``. The value of ``curdoc()`` inside the callback will be a
    specially wrapped version of |Document| that only allows safe operations,
    which are:

    * :func:`~bokeh.document.Document.add_next_tick_callback`
    * :func:`~bokeh.document.Document.remove_next_tick_callback`

    Only these may be used safely without taking the document lock. To make
    other changes to the document, you must add a next tick callback and make
    your changes to ``curdoc()`` from that second callback.

    Attempts to otherwise access or change the Document will result in an
    exception being raised.

    '''
    @wraps(func)
    def wrapper(*args, **kw):
        return func(*args, **kw)
    wrapper.nolock = True
    return wrapper