if(!ALL_MODES[mode]){throw new Error('Not a mode.');}
this.mode_=mode;this.defaultMetadata_={};this.defaultConstructor_=undefined;this.defaultTypeInfo_=undefined;this.frozen_=false;}
ExtensionRegistryOptions.prototype={freeze(){if(this.frozen_){throw new Error('Frozen');}
this.frozen_=true;},get mode(){return this.mode_;},get defaultMetadata(){return this.defaultMetadata_;},set defaultMetadata(defaultMetadata){if(this.frozen_){throw new Error('Frozen');}

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