docs: def find_or_create_mapping(self, mapped_class):
          """
          First calls :meth:`find_mapping` to check if a mapping for the given
          mapped class or any of its base classes has been created. If not, a
          new one is created with a default configuration, registered
          automatically and returned.
          """
          mapping = self.find_mapping(mapped_class)
          if mapping is None:
              mapping = self.create_mapping(mapped_class)
              self.set_mapping(mapping)
          return mapping