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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def get_schema(self, protocol_version):
 """Return the child schema for the correct const version."""

        const = get_const(protocol_version)
        custom_schema = vol.Schema({
            typ.value: const.VALID_SETREQ[typ]
            for typ in const.VALID_TYPES[const.Presentation.S_CUSTOM]})
        return custom_schema.extend({
            typ.value: const.VALID_SETREQ[typ]
            for typ in const.VALID_TYPES[self.type]})