Converting Raster format to ASCII raster.

        Args:
            raster_f: raster file.
            asc_f: output ASCII file.

def raster_to_asc(raster_f, asc_f):
        """Converting Raster format to ASCII raster.

        Args:
            raster_f: raster file.
            asc_f: output ASCII file.
        """
        raster_r = RasterUtilClass.read_raster(raster_f)
        RasterUtilClass.write_asc_file(asc_f, raster_r.data, raster_r.nCols, raster_r.nRows,
                                       raster_r.geotrans, raster_r.noDataValue)