code: func (node *Expression) HelperName() string {
  	path, ok := node.Path.(*PathExpression)
  	if !ok {
  		return ""
  	}
  
  	if path.Data || (len(path.Parts) != 1) || (path.Depth > 0) || path.Scoped {
  		return ""
  	}
  
  	return path.Parts[0]
  }
docs: // HelperName returns helper name, or an empty string if this expression can't be a helper.