def mark_users_as_churners(spark_df):
    """Creates a pyspark dataframe with userId and their corresponding churn nature. 1 if churned, 0 otherwise.

    Args:
        spark_df (pyspark.sql.dataframe.DataFrame): The pyspark dataframe containing event logs

    Returns:
        pyspark.sql.dataframe.DataFrame: Resultant pyspark dataframe
    """

    return spark_df.select("userId", "churned").distinct()