>>> from typing import Literal, Optional
>>> from xml.etree.ElementTree import canonicalize
>>> 
>>> from pydantic_xml import BaseXmlModel, element
>>> 
>>> class Product(BaseXmlModel, tag='Product'):
...     title: Optional[str] = element(tag='Title', default=None)
...     status: Optional[Literal['running', 'development']] = element(tag='Status', default=None)
...     launched: Optional[int] = element(tag='Launched', default=None)
... 
>>> product = Product(title="Starlink", status=None)
>>> print(product.to_xml(exclude_none=True, pretty_print=True).decode())
<Product>
  <Title>Starlink</Title>
</Product>

>>> from typing import Literal, Optional
>>> from xml.etree.ElementTree import canonicalize
>>> 
>>> from pydantic_xml import BaseXmlModel, element
>>> 
>>> class Product(BaseXmlModel, tag='Product'):
...     title: Optional[str] = element(tag='Title', default=None)
...     status: Optional[Literal['running', 'development']] = element(tag='Status', default=None)
...     launched: Optional[int] = element(tag='Launched', default=None)
... 
>>> product = Product(title="Starlink", status=None)
>>> print(product.to_xml(exclude_unset=True, pretty_print=True).decode())
<Product>
  <Title>Starlink</Title>
  <Status></Status>
</Product>