import re


def is_valid_policy_id(policy_id):
    """
    Validates a snapshot policy ID, also known as the snapshot policy "name".
    A valid snapshot policy name should look like: policy-00000001 - It should
    always start with "policy-" and end with 8 hexadecimal characters in lower
    case.

    :type policy_id: str
    :param policy_id: The snapshot policy name to be validated.

    :rtype: bool
    :return: True or False depending on whether policy_id passes validation.
    """
    if policy_id is None:
        return False

    match = re.match(r'^policy-[0-9a-f]{8}$', policy_id)

    if not match:
        return False

    return True