specifically over python, immutability in function passing is amazing for beginners and dealing with beginners.

How confident are you that the junior you just hired is operating correctly in the other_code module they're responsible for

    import other_code, as: other

    def f:
        my_dict = {"foo": 1, "bar": 2}
        other.function(my_dict)
        return my_dict["foo"] # ==>  you might be wrong about what's in my_dict