[python] Cannot pass keyword arguments to python.lib.Json.dumps

**Environment**
macOS 12.4
haxe 4.3.0-rc.a49b191

The following code throws the exception `TypeError: __init__() got an unexpected keyword argument '_hx_disable_getattr'`.

```
var json = python.Lib.anonAsDict({});
python.lib.Json.dumps(json, {separators: python.Tuple.Tuple2.make(",", ":")});
```

Start by reproducing the Haxe-to-Python example using python.lib.Json.dumps with the separators option. Then trace the python.lib.Json.dumps binding or entry point involved in keyword arguments. Done means the supplied snippet runs without the unexpected _hx_disable_getattr exception and preserves the requested separators.

Written by the indexing model from the issue text.