Prq bulk commands  DS 2019

see    https://jira.duraspace.org/browse/DS-2019
Correct me if I'm wrong, but it looks like you can avoid the casting of the "Object" for the three cases you describe by returning an array of strings. The equivalent of null could be an empty array, the equivalent of the single string could be an array with a single string. Making it a requirement for people to cast the return type of your method will make its use more error prone.