You are tasked with creating a Snowpark Python UDF that calculates the exponential moving average (EMA) of a time series dataset stored in a Snowflake table named 'SALES DATA'. The table has columns 'TIMESTAMP' (TIMESTAMP_NTZ) and 'SALES' (NUMBER). The EMA should be calculated for each product, identified by the 'PRODUCT ID' column. You want to optimize the calculation by using a Pandas DataFrame within the UDF and leveraging vectorized operations. Which of the following code snippets would be the MOST efficient and correct way to achieve this? Assume 'alpha' is a predefined float variable representing the smoothing factor.