def get_lat_lon_cols(df):
    """
    Get columns that contain (latitude, longitude) coordinates

    Parameters
    ----------
    df : pandas.DataFrame
        DataFrame to extract coordinates (lat, lon) from

    Returns
    -------
    lat_lon_cols : list
        Column names in df that correspond to the latitude and longitude
        coordinates. There must be a single unique set of latitude and
        longitude columns.
    """
    lat_lon_cols = ['latitude', 'longitude']
    lat = False
    lon = False
    for c in df.columns:
        if c.lower() in ['lat', 'latitude']:
            if lat:
                msg = ("Multiple possible latitude columns were found: "
                       "({}, {})!".format(lat_lon_cols[0], c))
                raise RuntimeError(msg)

            lat_lon_cols[0] = c
            lat = True
        elif c.lower() in ['lon', 'long', 'longitude']:
            if lon:
                msg = ("Multiple possible longitude columns were found: "
                       "({}, {})!".format(lat_lon_cols[1], c))
                raise RuntimeError(msg)

            lat_lon_cols[1] = c
            lon = True

    if not lat or not lon:
        msg = ("A valid pair of latitude and longitude columns could not be "
               "found in: {}!".format(df.columns))
        raise RuntimeError(msg)

    return lat_lon_cols