docs: def get_or_create(cls, name):
          """
          Return the instance of the class with the specified name. If it doesn't
          already exist, create it.
          """
          obj = cls.query.filter_by(name=name).one_or_none()
          if obj:
              return obj
          try:
              with session.begin_nested():
                  obj = cls(name=name)
                  session.add(obj)
                  session.flush()
              return obj
          except IntegrityError:
              log.debug('Collision when adding %s(name="%s"), returning existing object',
                        cls.__name__, name)
              return cls.query.filter_by(name=name).one()