code: function getCss(shapes, options) {
  	const spriteRelative = path.relative(options.styleOutput, options.spritePath);
  	return new CSS(shapes, {
  		nameSpace: options.nameSpace,
  		block: options.dirname,
  		separator: options.cssSeparator,
  		spriteRelative: path.normalize(spriteRelative).replace(/\\/g, '/')
  	}).getCss();
  }
docs: Get css code which corresponding to svg sprite
  
  @param  {Object} shapes
  @param  {Object} options
  @return {String} cssStr