code: function _getBoundingOffsetsRect (el, relativeParentEl) {
    var relativeParentElRect = relativeParentEl.getBoundingClientRect()
    var elRect = _getBoundingRect(el.getClientRects())
  
    var left = elRect.left - relativeParentElRect.left
    var top = elRect.top - relativeParentElRect.top
    return {
      left: left,
      top: top,
      right: relativeParentElRect.width - left - elRect.width,
      bottom: relativeParentElRect.height - top - elRect.height,
      width: elRect.width,
      height: elRect.height
    }
  }
docs: /*
  Calculate the bounding rect of a single element relative to a parent.
  
  The rectangle dimensions are calculated as the union of the given elements
  clientRects. A selection fragment, for example, may appear as a multi-line span
  element that consists of a single client rect per line of text in variable widths.
  
  @param {HTMLElement} el native DOM element to get the bounding rectangle for
  @param {HTMLElement} relativeParentEl native DOM element used as a reference point