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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 set_global_tracer(value):
 """Sets the global tracer. It is an error to pass ``None``. :param value: the :class:`Tracer` used as global instance. :type value: :class:`Tracer` """

    if value is None:
        raise ValueError('The global Tracer tracer cannot be None')

    global tracer, is_tracer_registered
    tracer = value
    is_tracer_registered = True