Converts a Python dictionary or other native data type into a valid XML string.
Supports item (`int`, `float`, `long`, `decimal.Decimal`, `bool`, `str`, `unicode`, `datetime`, `none` and other number-like objects) and collection (`list`, `set`, `tuple` and `dict`, as well as iterable and dict-like objects) data types, with arbitrary nesting for the collections. Items with a `datetime` type are converted to ISO format strings. Items with a `None` type become empty XML elements.