code: function generateETag(body, opt) {
  	if (_.isFunction(opt))
  		return opt.call(this, body);
  
  	let buf = !Buffer.isBuffer(body)
  		? Buffer.from(body)
  		: body;
  
  	return etag(buf, (opt === true || opt === "weak") ? { weak: true } : null);
  }
docs: Generate ETag from content.
  
  @param {any} body
  @param {Boolean|String|Function?} opt
  
  @returns {String}