get length(){return this.histograms_.size;}*[Symbol.iterator](){for(const hist of this.histograms_){yield hist;}}
getHistogramsNamed(name){return[...this].filter(h=>h.name===name);}
getHistogramNamed(name){const histograms=this.getHistogramsNamed(name);if(histograms.length===0)return undefined;if(histograms.length>1){throw new Error(`Unexpectedly found multiple histograms named "${name}"`);}
return histograms[0];}