code: def oid(self):
          
          m = re.match(r'^/api/storage-groups/[^/]*/storage-volumes/([^/]*)$',
                       self.uri)
          oid = m.group(1)
          return oid
docs: :term `unicode string`: The object ID of this storage volume.
          The object ID is unique within the parent storage group.
  
          Note that for storage volumes, the 'name' property is not unique and
          therefore cannot be used to identify a storage volume. Therefore,
          storage volumes provide easy access to the object ID, as a means to
          identify the storage volume in CLIs and other string-based tooling.