AWS/Linux: How to know if a device has File system on it

It is a common question which comes to me from people to understand how to know if a raw disk has file system on it or not. 

There can be multiple ways but in this blog I will talk about file command

File command can help you know if the FS is there or not?
How 
use file -s '/device_name'
if you get output like data: that means no FS
If there is any other output, it means FS is present.