docs: def getAsGrassAsciiGrid(self, session):
          """
          Retrieve the raster in the GRASS ASCII Grid format.
  
          Args:
              session (:mod:`sqlalchemy.orm.session.Session`): SQLAlchemy session object bound to PostGIS enabled database.
  
          Returns:
              str: GRASS ASCII string.
          """
          if type(self.raster) != type(None):
              # Make sure the raster field is valid
              converter = RasterConverter(sqlAlchemyEngineOrSession=session)
  
              return converter.getAsGrassAsciiRaster(tableName=self.tableName,
                                                     rasterIdFieldName='id',
                                                     rasterId=self.id,
                                                     rasterFieldName=self.rasterColumnName)