code: function insertContent(node, content) {
  	let inserted = insertContentIntoPlaceholder(node, content);
  	node.walk(child => inserted |= insertContentIntoPlaceholder(child, content));
  
  	if (!inserted) {
  		// no placeholders were found in node, insert content into deepest child
  		setNodeContent(findDeepestNode(node), content);
  	}
  
  	return node;
  }
docs: Inserts `content` into given `node`: either replaces output placeholders
  or inserts it into deepest child node
  @param  {Node} node
  @param  {String} content
  @return {Node}