code: def get_or_create(self, db_name):
          
          if not db_name in self:
              res = self.resource.put(db_name)
              if not res[0] == 201:
                  raise RuntimeError(
                      'Failed to create database "{}"'.format(db_name)
                  )
          return self[db_name]
docs: Creates the database named `db_name` if it doesn't already exist and
          return it