def open_imports(self, options, loaded_schemata):
        """
        Instruct all contained L{sxbasic.Import} children to import all of
        their referenced schemas. The imported schema contents are I{merged}
        in.

        @param options: An options dictionary.
        @type options: L{options.Options}
        @param loaded_schemata: Already loaded schemata cache (URL --> Schema).
        @type loaded_schemata: dict

        """
        for imp in self.imports:
            imported = imp.open(options, loaded_schemata)
            if imported is None:
                continue
            imported.open_imports(options, loaded_schemata)
            log.debug("imported:\n%s", imported)
            self.merge(imported)