code: function filterChildren(children, depth) {
  	if(depth == 1) {
  		let found = false;
  
  		for(let item of children) {
  			if(item.name == 'package.json') found = true;
  			if(item.name != 'src') item.enterDir = false;
  		}
  
  		if(!found) throw(new Error());
  	}
  
  	return(children);
  }
docs: Detect NPM package root directories by presence of a package.json file.
  Only enter a subdirectory called "src".
  Usable as a "before" callback for the walk function.
  @return Filtered list of directory contents.