nl_tokens: Gets the unique metadata keys defined on the target object . @param target The target object on which the metadata is defined . @param propertyKey ( Optional ) The property key for the target . @returns An array of unique metadata keys . @example
pl_tokens: function getOwnMetadataKeys ( target , propertyKey ) { if ( ! IsObject ( target ) ) throw new TypeError ( ) ; if ( ! IsUndefined ( propertyKey ) ) propertyKey = ToPropertyKey ( propertyKey ) ; return OrdinaryOwnMetadataKeys ( <mask> , propertyKey ) ; }