Returns a new RasterQuerySet with possibly warped/converted rasters.

        Keyword args:
        format -- raster file extension format as str
        geom -- geometry for masking or spatial subsetting
        srid -- spatial reference identifier as int for warping to

def warp(self, srid=None, format=None, geom=None):
        """Returns a new RasterQuerySet with possibly warped/converted rasters.

        Keyword args:
        format -- raster file extension format as str
        geom -- geometry for masking or spatial subsetting
        srid -- spatial reference identifier as int for warping to
        """
        clone = self._clone()
        for obj in clone:
            obj.convert(format, geom)
            if srid:
                fp = tempfile.NamedTemporaryFile(suffix='.%s' % format or '')
                with obj.raster() as r, r.warp(srid, fp.name) as w:
                    obj.image.file = fp
        return clone