It's a python script used to generate tags for a picture automatically using Google Vision API's label detection.
python tag.py <API-KEY-FOR-GOOGLE-VISION-API> <IMAGE-URL> <OUTPUT-FILE-PATH>
api-key for Google's Cloud Vision API can be generated by signing up at console.google.com and then enabling Cloud Vision API and generating credentials under 'API & Services'.
Example - python tag.py 12312341244241241241241 https://static.pexels.com/photos/248797/pexels-photo-248797.jpeg tags.txt
Output stored in tags.txt - #sea #coastalandoceaniclandforms #tropics #sky #caribbean #shore #azure #ocean #beach #coast