docs: def get_collection_for_cls(self, cls):
          """
          Returns the collection name for a given document class.
  
          :param cls: The document class for which to return the collection name.
  
          :returns: The collection name for the given class.
          """
          if cls not in self.classes:
              if issubclass(cls, Document) and cls not in self.classes and cls not in self.deprecated_classes:
                  self.autoregister(cls)
              else:
                  raise AttributeError("Unknown object type: %s" % cls.__name__)
          collection = self.classes[cls]['collection']
          return collection