def METHOD_NAME(before_metrics, after_metrics):
    """Given before and after metrics, return a dictionary describing
    their differences."""
    result = OrderedDict()
    for key in METRIC_KEYS:
        # Extract the leading byte count from the humanized string
        before = int(before_metrics[key].split()[0])
        after = int(after_metrics[key].split()[0])
        result[key] = human_readable_size(after - before, show_sign=True)
    return result