style(el, item) {
      if (item == null) return;
      for (const prop in stylesAttr) {
        let value = prop === 'font' ? fontFamily(item) : item[prop];
        if (value === values[prop]) continue;
        const name = stylesAttr[prop];
        if (value == null) {
          el.removeAttribute(name);
        } else {
          if (isGradient(value)) {
            value = gradientRef(value, this._defs.gradient, href());
          }
          el.setAttribute(name, value + '');
        }
        values[prop] = value;
      }
      for (const prop in stylesCss) {
        setStyle(el, stylesCss[prop], item[prop]);
      }
    }
Update the presentation attributes of an SVG element for a mark item.
@param {SVGElement} el - The SVG element.
@param {Item} item - The mark item.