¿Qué significa Multiple values on the sides of an assignment is not only to functions. ?

See a translation

Yes, this is about programming, Golang ;) I'm translating this article into Japanese but I couldn't really understand "to function"

The whole paragraph is:
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Function Return Values
Functions can return not only one single value, but multiple values. This seems to be a bad practice if not used properly. Python does that. Perl does that. It can be of good use. It is mainly used to return a value and a ‘nil’ or error code. This way the old habit of encoding the error into the returned type (usually returning -1 as error code and some non-negative value in case there is some meaningful return value as in C std library calls) is replaced with something much more readable.

Multiple values on the sides of an assignment is not only to functions. To swap two values you can write:

a,b = b,a
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I translated that part like this:
「代入の両側の、複数ある値は、関数に渡されるだけではない。二つの値を入れ替えるには、次のように書くことができる。」

Do you think 「関数に」 is correct?

Thank you for your help!!

Thank you so much for your help! I think I understood it :)
Sure, how can I send it to you?

Sorry, I noticed this now. I'm gonna send you soon :)
どういたしまして！