Hello!

I've encountered what might be a bug.

Up till now we had some working code that did this:

```
maps = self.style.map('TCombobox')
if maps:
    self.style.map('DateEntry', **maps)
```

Modifying a custom style to mimic the map of another. This has worked fine until Python 3.7, because the return value of `.map` is something that you can pass to `.map` as kw and it'll process it fine.

The return value of `.map` in Python 3.7 is something like this, for the `TCombobox`:

```
<class 'dict'>: {'focusfill': [('readonly', 'focus', 'SystemHighlight')], 'foreground': [('disabled', 'SystemGrayText'), ('readonly', 'focus', 'SystemHighlightText')], 'selectforeground': [('!focus', 'SystemWindowText')], 'selectbackground': [('!focus', 'SystemWindow')]}
```

Which is as you'd expect (and the docs say): a dictionary of properties to lists, where each list can contain multiple tuples describing the required state and final value of the property.

However in Python 3.8, the value returned by `.map` is this:

```
<class 'dict'>: {'focusfill': ['readonly focus', 'SystemHighlight'], 'foreground': ['disabled', 'SystemGrayText', 'readonly focus', 'SystemHighlightText'], 'selectforeground': ['!focus', 'SystemWindowText'], 'selectbackground': ['!focus', 'SystemWindow']}
```

The tuples are missing. This then causes a number of problems downstream, such as the final property values being split into the constituent letters instead of the values within each tuple.

This was likely caused by different versions of Tk.

It should be fixed now in issue42328. Style.map() should convert result to uniform representation on all versions and platforms, and accept input in different forms. Please check.