text: export class FilterByRange {
    constructor(opts ) {
      this.first = opts.first;
      this.last = opts.last;
      this.level = opts.level;
    }
  
    filter(d) {
      return d.__i[this.level] >= this.first.__i[this.level] && d.__i[this.level] <= this.last.__i[this.level];
    }
  }
  
  export class FilterByValue {
    constructor(opts ) {
      this.itemAttr = opts.itemAttr;
      this.sel = opts.sel;
    }
  
    filter(d) {
      return d[this.itemAttr] === this.sel[this.itemAttr];
    }
  }