src/vs/workbench/services/extensions/common/extensions.ts/ExtensionHostExtensions/containsExtension
class ExtensionHostExtensions:	public containsExtension(extensionId: ExtensionIdentifier): boolean {
		for (const myExtensionId of this._myExtensions) {
			if (ExtensionIdentifier.equals(myExtensionId, extensionId)) {
				return true;
			}
		}
		return false;
	}