"""Splits the URL into scheme and netloc.

This function parses the given URL and extracts the scheme (protocol) and netloc (host name). 
Both the scheme and netloc are returned in lowercase. If the URL does not include both a 
scheme and a netloc, a ValueError is raised.

Args:
    url (str): The URL to split. Must include both a protocol and a host name.

Returns:
    tuple[str, str]: A tuple containing the scheme and netloc of the URL, both in lowercase.

Raises:
    ValueError: If the URL does not include both a protocol and a host name.
"""
You should write code starting with:
from urllib.parse import urlparse

def _split_url(url: str) -> tuple[str, str]:
    # TODO: Implement this function
    pass

