def _get_kafka_config(config: dict) ->dict:
    """Returns configurations for a consumer instance

    Parameters
    ----------
    config: dict
        Dictionary of configurations

    Returns
    ----------
    kafka_config: dict
        Dictionary with configurations for creating an instance of
        a secured Kafka consumer
    """
    kafka_config = {}
    default_config = {'auto.offset.reset': 'earliest'}
    if 'username' in config and 'password' in config:
        kafka_config['security.protocol'] = 'sasl_plaintext'
        kafka_config['sasl.mechanism'] = 'SCRAM-SHA-512'
        kafka_config['sasl.username'] = config['username']
        kafka_config['sasl.password'] = config['password']
    kafka_config['group.id'] = config['group_id']
    kafka_config.update(default_config)
    if 'bootstrap.servers' in config:
        kafka_config['bootstrap.servers'] = config['bootstrap.servers']
    else:
        fink_servers = ['localhost:9093', 'localhost:9094', 'localhost:9095']
        kafka_config['bootstrap.servers'] = '{}'.format(','.join(fink_servers))
    return kafka_config
