def getBuild(number):
    """Return an IBuildStatus object for a historical build. Each build
        is numbered (starting at 0 when the Builder is first added),
        getBuild(n) will retrieve the Nth such build. getBuild(-n) will
        retrieve a recent build, with -1 being the most recent build
        started. If the Builder is idle, this will be the same as
        getLastFinishedBuild(). If the Builder is active, it will be an
        unfinished build. This method will return None if the build is no
        longer available. Older builds are likely to have less information
        stored: Logs are the first to go, then Steps."""
