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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 get_logout_url(service):
 """Get the configured logout URL for a given service identifier, if any."""

    for backend in _get_backends():
        try:
            return backend.get_logout_url(service)
        except AttributeError:
            raise NotImplementedError("%s.%s.get_logout_url() not implemented" % (
                backend.__class__.__module__, backend.__class__.__name__)
            )
    return None