I'm using getMultipleLeads to discover which leads have been added or updated recently to my given Marketo instance. One of the things I might want to do with those leads is to add them to a list -- again, using the SOAP API. I know that this will only succeed for leads that are in the same workspace as the list. Is there any way for me to discover via getMultipleLeads or any other API call which workspace(s) any given lead is in?