code: def __init_defaults(self, config):
          
  
          provider = self.__provider
  
          if provider == 'sqlite':
              config.setdefault('dbname', ':memory:')
              config.setdefault('create_db',  True)
          elif provider == 'mysql':
              config.setdefault('port', 3306)
              config.setdefault('charset', 'utf8')
          elif provider == 'postgres':
              config.setdefault('port', 5432)
          elif provider == 'oracle':
              config.setdefault('port', 1521)
          else:
              raise ValueError('Unsupported provider "{}"'.format(provider))
  
          if provider != 'sqlite':
              config.setdefault('host', 'localhost')
              config.setdefault('user', None)
              config.setdefault('password', None)
              config.setdefault('dbname', None)
docs: Initializes the default connection settings.