Example Provided Error

[RoyalCoder88]

Hi, thanks for your great package, I got the provided example from GitHub but I get this error:

Exception has occurred.
FlutterError (There are multiple heroes that share the same tag within a subtree.
Within each subtree for which heroes are to be animated (i.e. a PageRoute subtree), each Hero must have a unique non-null tag.
In this case, multiple heroes had the following tag: <default FloatingActionButton tag>
# Here is the subtree for one of the offending heroes: Hero)

*also can you guide me on how can I achieve saving for the StackBoard data for example like a .json? Thanks in advance!