You can put arbitrary metadata on functions, classes and other things that are basically objects in in Python. If you write

   def somefunction(x):
      ... body ...

you can later write

   somefunction.specialmetadata = "a value"

so what you can do is fairly unlimited. You can't write, however

   x = 4
   x.metavalue = 3

as the int isn't a general object. Even if you did the metadata would apply to the value (the '4') and not the variable (the 'x')

Clojure supports metadata:

https://clojure.org/reference/metadata