def ping():
    """Attempt to contact the worker and see if it is still alive. This
        returns a Deferred which fires with either True (the worker is still
        alive) or False (the worker did not respond). As a side effect, adds an
        event to this builder's column in the waterfall display containing the
        results of the ping. Note that this may not fail for a long time, it is
        implemented in terms of the timeout on the underlying TCP connection."""
