I don't quite understand why they forbid this from being used in functions.

I mean I get why that makes the most sense in most scenarios, but it is not as if the problem of having to choose between declaring dependencies up front or deferring expensive imports until needed does not happen in functions.

Take for instance a function that quickly fails because the arguments are incorrect, it might do a whole bunch of imports that only make sense for that function but which are made immediately obsolete.

It feels like it is forbidden just because someone thought it wasn't a good coding style but to me there is no obvious reason it couldn't work.