Called by ``docx.opc.package.PartFactory`` to load an image part from
        a package being opened by ``Document(...)`` call.

def load(cls, partname, content_type, blob, package):
        """
        Called by ``docx.opc.package.PartFactory`` to load an image part from
        a package being opened by ``Document(...)`` call.
        """
        return cls(partname, content_type, blob)