reset(labels, timestamp) {
		const hash = this.hashingLabels(labels);
		const item = this.values.get(hash);
		if (item) {
			this.resetItem(item, timestamp);
			this.changed(null, labels, timestamp);
		}
	}
Reset item by labels.

@param {Object} labels
@param {Number?} timestamp
@returns
@memberof HistogramMetric