Converts a lat/lon pair to a comma-separated string.

    For example:

    sydney = {
        "lat" : -33.8674869,
        "lng" : 151.2069902
    }

    convert.latlng(sydney)
    # '-33.8674869,151.2069902'

    For convenience, also accepts lat/lon pair as a string, in
    which case it's returned unchanged.

    :param arg: The lat/lon pair.
    :type arg: string or dict or list or tuple

def latlng(arg):
    """Converts a lat/lon pair to a comma-separated string.

    For example:

    sydney = {
        "lat" : -33.8674869,
        "lng" : 151.2069902
    }

    convert.latlng(sydney)
    # '-33.8674869,151.2069902'

    For convenience, also accepts lat/lon pair as a string, in
    which case it's returned unchanged.

    :param arg: The lat/lon pair.
    :type arg: string or dict or list or tuple
    """
    if is_string(arg):
        return arg

    normalized = normalize_lat_lng(arg)
    return "%s,%s" % (format_float(normalized[0]), format_float(normalized[1]))