code: function convertCSS(editor, node, pos) {
  	if (node.type !== 'property' || !containsPoint(node.valueToken, pos)) {
  		return Promise.reject('Unsupported CSS context for data:URL convertion');
  	}
  
  	// First, we have to find which part of (possibly) comma-separated value
  	// contains given point. Also, `.parsedValue` returns a fully parsed value,
  	// unlike `.value`, wich contains only a textual representation of full
  	// property value
  	const valuePart = node.parsedValue.find(item => containsPoint(item, pos));
  	const urlToken = findTokenForPoint(valuePart, pos, 'url');
  	if (urlToken) {
  		let urlValue = urlToken.item(0);
  		if (urlValue && urlValue.type === 'string') {
  			// get unquoted value
  			urlValue = urlValue.item(0);
  		}
  
  		const src = urlValue ? urlValue.valueOf() : '';
  		if (!src) {
  			return Promise.reject(`No valid url() token in "${node.name}" property`);
  		}
  
  		const replacementRange = getRange(urlValue);
  		const m = src.match(reIsDataURL);
  
  		return m
  			? saveAsFile(editor, src.slice(m[0].length), replacementRange)
  			: convertToDataUrl(editor, src, replacementRange);
  	}
  }
docs: Converts to/from data:URL contents of `src` attribute of given CSS node
  @param  {TextEditor} editor
  @param  {Node}       node
  @param  {Point}      pos
  @return {Promise}