Below is a dialogue between software developers, the first one used ChatGPT in his solution of code task and makes a comment,   the second one gives him reply on his solution. Write a reply that appropriately answers the comment.

### Comment:
likely the best thing to do is to use collections.unmodifiablemap instead of implement your own immutable class### Reply:
weve investigated that and the main problem was that when copying an unmodifiablemap during a .map for example, the return type is again modifiable. this custom class made sure that it always returns immutable maps.