How to remove first part of string so I can decode it. flutter/dart

I’m getting bytes property from api as a string but it has prefix and it looks like this:
data:application/octet-stream;base64,JVBERi0xLjcNJeLjz9MNCjEgMCBvYmoNPDwv.... So my question is how can i remove this part data:application/octet-stream;base64, from string so I can decode the rest of same string.

>Solution :

Another way to do it is like:

final str = "data:application/octet-stream;base64,JVBERi0xLjcNJeLjz9MNCjEgMCBvYmoNPDwv0w";
final desiredStr = str.substring(str.indexOf(',') + 1);