Initializes the default connection settings.

def __init_defaults(self, config):
        """Initializes the default connection settings."""

        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)