Gets a row set of the data source for a specified parent key.
Returns a Rowset object. If parent-key refers to an existing Rowset object in the data source, then the details of this Rowset are returned in a Rowset object. Otherwise, the return value is undefined.
The required parent-key must be one of the following:
•The literal string 'current'. This refers to the currently active row set of the data source.
•Any other key-string representing the row set's parent key. This must be an exact match to any Rowset object in the data source object in the data layer.
•An object that is a struct specifying one or more parent keys for at least one data source. This object is transformed to the corresponding key-string at runtime.