NDI_OPENDATABASE - open the database associated with an session
DB = ndi.database.fun.opendatabase(DATABASE_PATH, SESSION_UNIQUE_REFERENCE)
Searches the file path DATABASE_PATH for any known databases in NDI_DATABASEHIERACHY. If it finds a datbase of subtype ndi.database, then it is opened and returned in DB.
If it finds no databases, then it tries to create a new database following the order in the hierarchy.
Otherwise, DB is empty.