[rockemsockem]

That example actually holds with what the parent comment said. You aren't trying to modify d exactly, you're modifying d's contents.

  Python 3.8.10 (default, Jun 22 2022, 20:18:18) 
  [GCC 9.4.0] on linux
  Type "help", "copyright", "credits" or "license" for more 
  information.
  >>> def f(d):
  ...     d = {'foo': 'bar'}
  ... 
  >>> a = {}
  >>> f(a)
  >>> a
  {}

does not modify the passed in dictionary, because the reference 'd' itself is passed by value. So the function doesn't change what d references for the caller. Java works the same way.