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.

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)