finish.style.visibility = 'hidden'
        this.container.appendChild(finish)
        // Appends dynamically loaded lines to existing line elements.
        this.lines = [...this.container.querySelectorAll(`[${this.pfx}]`)].concat(this.lineData);
        for (let line of this.lines) {
            line.style.visibility = 'hidden'
            this.container.appendChild(line)
        }