Aggregate dot SQL

The following code uses SQL to set the value of a dataframe called df.

df = spark.sql("""
SELECT *, 
LEAD(time,1) OVER(PARTITION BY train_id ORDER BY time) AS time_next 
FROM schedule
""")

The LEAD clause has an equivalent function in pyspark.sql.functions.
The PARTITION BY, and ORDER BY clauses each have an equivalent dot notation function that is called on the Window object.
The following imports are available:
- from pyspark.sql import Window
- from pyspark.sql.functions import lead

Create a dataframe called dot_df that contains the identical result as df, using dot notation instead of SQL.