This is a decorator which can be used to mark functions
    as deprecated. It will result in a warning being emitted
    when the function is used.

def _wrap(func, msg):
    """This is a decorator which can be used to mark functions
    as deprecated. It will result in a warning being emitted
    when the function is used."""

    @functools.wraps(func)
    def new_func(*args, **kwargs):
        warnings.simplefilter('always', DeprecationWarning)     # turn off filter
        warnings.warn(msg, category=DeprecationWarning, stacklevel=2)
        warnings.simplefilter('default', DeprecationWarning)    # reset filter
        return func(*args, **kwargs)
    return new_func