Having issues running examples/file-viewer

[adarsh123456789]

Hi,
I was trying out the example from https://github.com/bblfsh/uast-viewer/tree/master/examples/file-viewer
after running the given steps I get a clean window stating:

Compiled successfully!

You can now view file-viewer in the browser.

Local: http://localhost:3000/
On Your Network: http://172.17.0.2:3000/

Note that the development build is not optimized.
To create a production build, use yarn build.

I visited http://172.17.0.2:3000/ , http://localhost:3000/ & this http://localhost:8080/,
http://localhost:3000/ page doesn't load up, the remaining 2 links are leading to a similar looking React App where file upload can take place.

then for uploading a UAST file, I created a file with the below content and saved it as .json:
file.json:

{ "code":
"def fizzbuzz(n):

if n % 3 == 0 and n % 5 == 0:
    return 'FizzBuzz'
elif n % 3 == 0:
    return 'Fizz'
elif n % 5 == 0:
    return 'Buzz'
else:
    return str(n)

print "\n".join(fizzbuzz(n) for n in xrange(1, 21))",
"lang": "PYTHON",
"uast": {//*[@ROLE='Number' and @ROLE='Literal']}
}

and once I upload the file.json file I don't see any changes coming up rather than the filename appearing near the "Choose File" button.

I tried this on both the links:
http://172.17.0.2:3000/
http://localhost:8080/
leading to same results.

I am not quite sure if I have missed out something, please help me on this.