def measurement_id(measurement_uuid: str, agent_uuid: str) -> str:
    """
    Measurement IDs used by Iris
    >>> measurement_id("57a54767-8404-4070-8372-ac59337b6432", "e6f321bc-03f1-4abe-ab35-385fff1a923d")
    '57a54767-8404-4070-8372-ac59337b6432__e6f321bc-03f1-4abe-ab35-385fff1a923d'

    Measurement IDs used by Diamond-Miner test data
    >>> measurement_id("test_nsdi_example", "")
    'test_nsdi_example'
    """
    s = measurement_uuid
    if agent_uuid:
        s += f"__{agent_uuid}"
    return s