code: def _raster_layers(self):
          
          layers = []
  
          raster_datasource = gdal.Open(self.uri.absoluteFilePath())
          if raster_datasource:
              subdatasets = raster_datasource.GetSubDatasets()
              if len(subdatasets) == 0:
                  metadata = raster_datasource.GetMetadata()
                  layers.append(metadata['IDENTIFIER'])
              else:
                  for subdataset in subdatasets:
                      layers.append(subdataset[0].split(':')[2])
  
          return layers
docs: Return a list of raster layers available.
  
          :return: List of raster layers available in the geopackage.
          :rtype: list
  
          .. versionadded:: 4.0