When exporting instance, holdings and items data, if the instance has mulitple holdings and the holdings have multiple items associated with them, then the items should be grouped by holdings when the record is exported.
Steps to Reproduce:
1. Create a mapping profile, for example:
2. Create a job profile that references the mapping profile.
3. Set the inventory so there is an instance with multiple holdings and holdings have multiple items. For example:
4. Export the record using the mapping profile from the step 1.
In the MARC record that was generated, items are grouped by holdings:
Holidings records are displayed first, followed by items: