turn array Item schema data.
	 */
	public function get_item_schema() {
		if ( $this->schema ) {
			return $this->add_additional_fields_schema( $this->schema );
		}

		$schema = array(
			'$schema'    => 'http://json-schema.org/draft-04/schema#',
			'title'      => "{$this->parent_post_type}-revision",
			'type'       => 'object',
			// Base properties for every revision.
			'properties' => array(

				/*
				 * Adds settings and styles from the WP_REST_Revisions_Controller item fields.
				 * Leaves out GUID as global styles shouldn't be accessible via URL.
				 */
				'author'       => array(
					'description' => __( 'The ID for the author of the revision.' ),
					'type'        => 'integer',
					'context'     => array( 'view', 'edit', 'embed' ),
				),
				'date'         => array(
					'description' => __( "The date the revision was published, in the site's timezone." ),
					'type'        => 'string',
					'format'      => 'date-time',
					'context'     => array( 'view', 'edit', 'embed' ),
				),
				'date_gmt'     => array(
					'description' => __( 'The date the revision was published, as GMT.' ),
					'type'        => 'string',
					'format'      => 'date-time',
					'context'     => array( 'view', 'edit' ),
				),
				'id'           => array(
					'description' => __( 'Unique identifier for the revision.' ),
					'type'        => 'integer',
					'context'     => array( 'view', 'edit', 'embed' ),
				),
				'modified'     => array(
					'description' => __( "The date the revision was last modified, in the site's timezone." ),
					'type'        => 'string',
					'format'      => 'date-time',
					'context'     => array( 'view', 'edit' ),
				),
				'modified_gmt' => array(
					'description' => __( 'The date the revision was last modified, as GMT.' ),
					'type'        => 'string',
					'format'      => 'date-time',
					'context'     => array( 'view', 'edit' ),
				),
				'parent'       => array(
					'description' => __( 'The ID for the parent of the revision.' ),
					'type'        => 'integer',
					'context'     => array( 'view', 'edit', 'embed' ),
				),

				// Adds settings and styles from the WP_REST_Global_Styles_Controller parent schema.
				'styles'       => array(
					'description' => __( 'Global styles.' ),
					'type'        => array( 'object' ),
					'context'     => array( 'view', 'edit' ),
				),
				'settings'     => array(
					'description' => __( 'Global settings.' ),
					'type'        => array( 'object' ),
					'context'     => array( 'view', 'edit' ),
				),
			),
		);

		$this->schema = $schema;

		return $this->add_additional_fields_schema( $this->schema );
	}

	/**
	 * Checks if a given request has access to read a single global style.
	 *
	 * @since 6.3.0
	 *
	 * @param WP_REST_Request $request Full details about the request.
	 * @return true|WP_Error True if the request has read access, WP_Error object otherwise.
	 */
	public function get_item_permissions_check( $request ) {
		$post = $this->get_parent( $request['parent'] );
		if ( is_wp_error( $post ) ) {
			return $post;
		}

		/*
		 * The same check as WP_REST_Global_Styles_Controller::get_item_permissions_check.
		 */
		if ( ! current_user_can( 'read_post', $post->ID ) ) {
			return new WP_Error(
				'rest_cannot_view',
				__( 'Sorry, you are not allowed to view revisions for this global style.' ),
				array( 'status' => rest_authorization_required_code() )
			);
		}

		return true;
	}

	/**
	 * Gets the parent post, if the ID is valid.
	 *
	 * Duplicate of WP_REST_Revisions_Controller::get_parent.
	 *
	 * @since 6.3.0
	 *
	 * @param int $parent_post_id Supplied ID.
	 * @return WP_Post|WP_Error Post object if ID is valid, WP_Error otherwise.
	 */
	protected function get_parent( $parent_post_id ) {
		$error = new WP_Error(
			'rest_post_invalid_parent',
			__( 'Invalid post parent ID.' ),
			array( 'status' => 404 )
		);

		if ( (int) $parent_post_id <= 0 ) {
			return $error;
		}

		$parent_post = get_post( (int) $parent_post_id );

		if ( empty( $parent_post ) || empty( $parent_post->ID )
			|| $this->parent_post_type !== $parent_post->post_type
		) {
			return $error;
		}

		return $parent_post;
	}
}