private static ExtensionContext.Namespace namespace(
      ExtensionContext extensionContext, Class clazz) {
    return ExtensionContext.Namespace.create(clazz, extensionContext);
  }
private static ExtensionContext . Namespace namespace ( ExtensionContext extensionContext , Class clazz ) { return ExtensionContext . Namespace . create ( clazz , extensionContext ) ; }
Creates a {@link ExtensionContext.Namespace} in which extension state is stored on creation for
post execution destruction. Storing data in a custom namespace prevents accidental cross
pollination of data between extensions and between different invocations within the lifecycle
of a single extension.

@param extensionContext the <em>context</em> in which the current test or container is being
executed
@return a {@link ExtensionContext.Namespace} describing the scope for an extension