_update(mdef, el, item) {
      // set dom element and values cache
      // provides access to emit method
      element$1 = el;
      values = el.__values__;

      // apply aria-specific properties
      ariaItemAttributes(emit, item);

      // apply svg attributes
      mdef.attr(emit, item, this);

      // some marks need special treatment
      const extra = mark_extras[mdef.type];
      if (extra) extra.call(this, mdef, el, item);

      // apply svg style attributes
      // note: element state may have been modified by 'extra' method
      if (element$1) this.style(element$1, item);
    }
Update the attributes of an SVG element for a mark item.
@param {object} mdef - The mark definition object
@param {SVGElement} el - The SVG element.
@param {Item} item - The mark item.