def stringify(metrics_headers=()):
    """Convert the provided metrics headers to a string.

    Iterate over the metrics headers (a dictionary, usually ordered) and
    return a properly-formatted space-separated string
    (e.g. foo/1.2.3 bar/3.14.159).
    """
    metrics_headers = collections.OrderedDict(metrics_headers)
    return ' '.join(['%s/%s' % (k, v) for k, v in metrics_headers.items()])
Convert the provided metrics headers to a string.

    Iterate over the metrics headers (a dictionary, usually ordered) and
    return a properly-formatted space-separated string
    (e.g. foo/1.2.3 bar/3.14.159).