Source

File: wp-includes/rest-api/endpoints/class-wp-rest-controller.php

public function create_item( $request ) {
		return new WP_Error(
			'invalid-method',
			/* translators: %s: Method name. */
			sprintf( __( "Method '%s' not implemented. Must be overridden in subclass." ), __METHOD__ ),
			array( 'status' => 405 )
		);
	}