MAINT: use copy utility from #19014 in cluster

[lucascolley]

Reference issue

n/a

What does this implement/fix?

Applies the copy utility from #19014 to the code added to cluster in #18668.

Additional information

cc: @andyfaff

[lucascolley]

CI Lint:

scipy/cluster/hierarchy.py:4021:8: E721 Do not compare types, use `isinstance()`

The offending code:

if type(i) is not int:

Let me know whether that fix belongs in this PR or a separate one.

[andyfaff]

I don't know why it's complaining about the lint, those lines haven't been touched. Yes, can you fix the lint issue, it'll prevent it coming up again.
Otherwise LGTM.

[lucascolley]

Lint is happy now. I changed to using isinstance on two other lines as well just in case.

[andyfaff]

Do you know what's going on with the docs build?

[lucascolley]

I have no idea... there aren't any changes to the docs here.

Edit: #19061

[lucascolley]

This should be ready to merge now that the docs build is fixed!

[andyfaff]

thank you @lucascolley