Value of type 'StorageMetadata' has no member 'downloadURL'

[takaaa220]

In File.swift l.130 return self.metadata?.downloadURL() , the above error has occurred.

   /// DownloadURL
    public var downloadURL: URL? {
        if let url: URL = self._downloadURL {
            return url
        }
        return self.metadata?.downloadURL()
    }

What should I change this code?