Return all signal handlers that are currently still alive for the
    input `signal`.

    Args:
        signal: A signal name.

    Returns:
        A list of callable receivers for the input signal.

def __live_receivers(signal):
    """Return all signal handlers that are currently still alive for the
    input `signal`.

    Args:
        signal: A signal name.

    Returns:
        A list of callable receivers for the input signal.
    """
    with __lock:
        __purge()
        receivers = [funcref() for funcref in __receivers[signal]]

    return receivers