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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 labels(self, *labelvalues, **labelkwargs):
 """Return the child for the given labelset. All metrics can have labels, allowing grouping of related time series. Taking a counter as an example: from prometheus_client import Counter c = Counter('my_requests_total', 'HTTP Failures', ['method', 'endpoint']) c.labels('get', '/').inc() c.labels('post', '/submit').inc() Labels can also be provided as keyword arguments: from prometheus_client import Counter c = Counter('my_requests_total', 'HTTP Failures', ['method', 'endpoint']) c.labels(method='get', endpoint='/').inc() c.labels(method='post', endpoint='/submit').inc() See the best practices on [naming](http://prometheus.io/docs/practices/naming/) and [labels](http://prometheus.io/docs/practices/instrumentation/#use-labels). """

        if not self._labelnames:
            raise ValueError('No label names were set when constructing %s' % self)

        if self._labelvalues:
            raise ValueError('%s already has labels set (%s); can not chain calls to .labels()' % (
                self,
                dict(zip(self._labelnames, self._labelvalues))
            ))

        if labelvalues and labelkwargs:
            raise ValueError("Can't pass both *args and **kwargs")

        if labelkwargs:
            if sorted(labelkwargs) != sorted(self._labelnames):
                raise ValueError('Incorrect label names')
            labelvalues = tuple(unicode(labelkwargs[l]) for l in self._labelnames)
        else:
            if len(labelvalues) != len(self._labelnames):
                raise ValueError('Incorrect label count')
            labelvalues = tuple(unicode(l) for l in labelvalues)
        with self._lock:
            if labelvalues not in self._metrics:
                self._metrics[labelvalues] = self.__class__(
                    self._name,
                    documentation=self._documentation,
                    labelnames=self._labelnames,
                    unit=self._unit,
                    labelvalues=labelvalues,
                    **self._kwargs
                )
            return self._metrics[labelvalues]