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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def get_fn(elev, name=None):
 """ Determines the standard filename for a given GeoTIFF Layer. Parameters elev : GdalReader.raster_layer A raster layer from the GdalReader object. name : str (optional) An optional suffix to the filename. Returns ------- fn : str The standard <filename>_<name>.tif with suffix (if supplied) """

    gcs = elev.grid_coordinates
    coords = [gcs.LLC.lat, gcs.LLC.lon, gcs.URC.lat, gcs.URC.lon]
    return get_fn_from_coords(coords, name)