import requests


def get_options(server):
    """Retrieve all allowed HTTP verbs/methods."""
    try:
        response = requests.options(
            server, allow_redirects=False, verify=False, timeout=5
        )
    except (
        requests.exceptions.ConnectionError,
        requests.exceptions.MissingSchema,
    ):
        return None

    try:
        return response.headers["Allow"]
    except KeyError:
        return None