-Returns the data associated with the given I<$name>/I<$key> pair or an empty
-list if no data has been stored under this tupel before..
+Returns a list of all the keys defined for this object. If one field is given
+the list will be sorted by that field's values, if more fields are given the
+list is sorted with the first field taking precedence over the others. If no
+field is supplied the order is undefined.