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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 _track(metric_type, metric_call, metric_kwargs, name, description, labels, registry, before=None):
 """ Internal method decorator logic. :param metric_type: the type of the metric from the `prometheus_client` library :param metric_call: the invocation to execute as a callable with `(metric, time)` :param metric_kwargs: additional keyword arguments for creating the metric :param name: the name of the metric :param description: the description of the metric :param labels: a dictionary of `{labelname: callable_or_value}` for labels :param before: an optional callable to invoke before executing the request handler method accepting the single `metric` argument :param registry: the Prometheus Registry to use """


        if labels is not None and not isinstance(labels, dict):
            raise TypeError('labels needs to be a dictionary of {labelname: callable}')

        label_names = labels.keys() if labels else tuple()
        parent_metric = metric_type(
            name, description, labelnames=label_names, registry=registry,
            **metric_kwargs
        )

        def argspec(func):
            if hasattr(inspect, 'getfullargspec'):
                return inspect.getfullargspec(func)
            else:
                return inspect.getargspec(func)

        def label_value(f):
            if not callable(f):
                return lambda x: f
            if argspec(f).args:
                return lambda x: f(x)
            else:
                return lambda x: f()

        label_generator = tuple(
            (key, label_value(call))
            for key, call in labels.items()
        ) if labels else tuple()

        def get_metric(response):
            if label_names:
                return parent_metric.labels(
                    **{key: call(response) for key, call in label_generator}
                )
            else:
                return parent_metric

        def decorator(f):
            @functools.wraps(f)
            def func(*args, **kwargs):
                if before:
                    metric = get_metric(None)
                    before(metric)

                else:
                    metric = None

                start_time = default_timer()
                try:
                    response = f(*args, **kwargs)
                except HTTPException as ex:
                    response = ex
                except Exception as ex:
                    response = make_response('Exception: %s' % ex, 500)

                total_time = max(default_timer() - start_time, 0)

                if not metric:
                    response_for_metric = response

                    if not isinstance(response, Response):
                        if request.endpoint == f.__name__:
                            # we are in a request handler method
                            response_for_metric = make_response(response)

                    metric = get_metric(response_for_metric)

                metric_call(metric, time=total_time)
                return response

            return func

        return decorator