function fillDocumentByCloningElement (elem, count) {
    const elemId = elem.getAttribute('id') + '-'
    for (let index = 0; index < count; index++) {
      const clone = elem.cloneNode(true) // t: deep clone
      // Make sure you set a unique ID like a real document.
      clone.setAttribute('id', elemId + index)
      const { parentNode } = elem
      parentNode.append(clone)
    }
  }
Toward performance testing, fill document with clones of element.
@param {SVGElement} elem
@param {Integer} count
@returns {void}