In time series analysis with Pandas, when using the resample method for aggregating daily sales data, what does the $\text{'}$W$\text{'}$ in df$\_$ex$.$resample$(\text{'}$W$).$sum$)$ signify?Aggregation is to be done based on weekdays.The resulting frequency conversion is to weekly totals.The data is to be windowed into $\text{'}$W$\text{'}$ equal parts.The aggregation will include only the workdays of the week.