deltaSource(newValue) {
    if (newValue === 'page' || newValue === 'client') {
      this.options.deltaSource = newValue;
      return this;
    }

    return this.options.deltaSource;
  }
Returns or sets the mouse coordinate types used to calculate the
movement of the pointer.

@param {string} [newValue] Use 'client' if you will be scrolling while
interacting; Use 'page' if you want autoScroll to work
@return {string | object} The current deltaSource or this Interactable