extensions/json-language-features/client/src/node/schemaCache.ts/JSONSchemaCache/getSchema
class JSONSchemaCache:	async getSchema(schemaUri: string, etag: string, etagValid: boolean): Promise<string | undefined> {
		const cacheEntry = this.cacheInfo[schemaUri];
		if (cacheEntry) {
			if (cacheEntry.etag === etag) {
				return this.loadSchemaFile(schemaUri, cacheEntry, etagValid);
			} else {
				this.deleteSchemaFile(schemaUri, cacheEntry);
			}
		}
		return undefined;
	}