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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_backend_instance(self, backend: BackendDefinitionType) -> BaseBackend: """ Returns a backend instance, either from the argument or from the settings. :raise ArcaMisconfigured: If the instance is not a subclass of :class:`BaseBackend` """

        if backend is NOT_SET:
            backend = self.get_setting("backend", "arca.CurrentEnvironmentBackend")

        if isinstance(backend, str):
            backend = load_class(backend)

        if callable(backend):
            backend = backend()

        if not issubclass(type(backend), BaseBackend):
            raise ArcaMisconfigured(f"{type(backend)} is not an subclass of BaseBackend")

        return backend