The file has been corrupted or is not a valid notebook file. 
SyntaxError: Unexpected token 'v', "version ht"... is not valid JSON
CustomError: SyntaxError: Unexpected token 'v', "version ht"... is not valid JSON
    at new pM (https://ssl.gstatic.com/colaboratory-static/common/73c56aa57e34a745ba3920b56acf3b31/external_binary.js:2445:164)
    at ua.program_ (https://ssl.gstatic.com/colaboratory-static/common/73c56aa57e34a745ba3920b56acf3b31/external_binary.js:2428:514)
    at ya (https://ssl.gstatic.com/colaboratory-static/common/73c56aa57e34a745ba3920b56acf3b31/external_binary.js:16:57)
    at ua.next_ (https://ssl.gstatic.com/colaboratory-static/common/73c56aa57e34a745ba3920b56acf3b31/external_binary.js:14:195)
    at kaa.next (https://ssl.gstatic.com/colaboratory-static/common/73c56aa57e34a745ba3920b56acf3b31/external_binary.js:17:48)
    at b (https://ssl.gstatic.com/colaboratory-static/common/73c56aa57e34a745ba3920b56acf3b31/external_binary.js:17:309)
 OK