Write a function called generate$\_$descriptors$($df$)$ which takes in the DataFrame you loaded from Question$1$ and returns a dataframe of all unique ticket descriptions and how frequent they are $($e$.$g$.$ it will tell you how many "HANDICAP" or $"$NO PERMITS U$/$M$"$ tickets have been issued$)$ for each of the following three time periods: morning $(3$ am to $11$:$59$ am$),$ afternoon $(12$ pm $-5$:$59$ pm$),$ and evening $(6$ pm $-2$:$59$ am$).$