start(time) {
		this.logger.debug(`[${this.id}] Span '${this.name}' is started.`);

		this.startTime = time || Date.now();
		this.startTicks = perf.now();
		// console.log(`"${this.name}" start time: ${this.startTime}`);

		this.tracer.spanStarted(this);

		return this;
	}
Start span.

@param {Number?} time
@returns {Span}
@memberof Span