def describe_inplane_accel(metadata: dict) -> str:
    """Generate description of in-plane acceleration factor, if any."""
    return (
        "in-plane acceleration factor={}".format(
            metadata["ParallelReductionFactorInPlane"]
        )
        if metadata.get("ParallelReductionFactorInPlane", 1) > 1
        else ""
    )