title: How to get type of the file from the Google Cloud Storage based on its blobkey?
body: <p>I have the blobkey of the file stored in the Google Cloud Storage. This is the only information I have. Having this information, I can read the file (but I don't know and can not get its filename). Is there any way to get the file type or read its metadata (<code>Content type</code>, for ex., <code>image/jpeg</code>) either from the file content or from the Google Cloud Storage? It will allow me to assign correct file extensions (filename is not so important, so standard names like <code>noname.jpg</code>, <code>noname.png</code>, <code>noname.pdf</code> will be OK).  </p>