code: func (apiDef *APIDefinition) FindLibFile(name string) (string, string) {
  	// search in it's document
  	if filename, ok := apiDef.Uses[name]; ok {
  		return "", filename
  	}
  
  	// search in included libraries
  	for _, lib := range apiDef.Libraries {
  		if filename, ok := lib.Uses[name]; ok {
  			return filepath.Dir(lib.Filename), filename
  		}
  	}
  	return "", ""
  }
docs: // FindLibFile find lbrary dir and file by it's name
  // we also search from included library