src/vs/workbench/contrib/notebook/browser/notebook.contribution.ts/RegisterSchemasContribution/registerMetadataSchemas
class RegisterSchemasContribution:	private registerMetadataSchemas(): void {
		const jsonRegistry = Registry.as<IJSONContributionRegistry>(JSONExtensions.JSONContribution);
		const metadataSchema: IJSONSchema = {
			properties: {
				['language']: {
					type: 'string',
					description: 'The language for the cell'
				},
				['inputCollapsed']: {
					type: 'boolean',
					description: `Whether a code cell's editor is collapsed`
				},
				['outputCollapsed']: {
					type: 'boolean',
					description: `Whether a code cell's outputs are collapsed`
				}
			},
			// patternProperties: allSettings.patternProperties,
			additionalProperties: true,
			allowTrailingCommas: true,
			allowComments: true
		};

		jsonRegistry.registerSchema('vscode://schemas/notebook/cellmetadata', metadataSchema);
	}