Explain in detail what the following code is doing:     import sys """ This functions build the title-actors dictionary.  The keys are movie titles, and the values are the cast lists of each movie.""" def make_title_dict():         titleActorDict = {} # create an empty dict (movie title -> key, list of actor(s) )         with open("imdb.txt", "r") as fHandle: # open file for reading         lines = fHandle.readlines() # list of lines from the input file           for index in range (0, len(lines), 2):         title = lines[index].strip().lower() # movie name -> key         actor = lines[index+1].strip().lower() # actor name -> value                if title in titleActorDict:  # already in Dict             titleActorDict[title].append(actor)              else :  # its not in the Dict yet              titleActorDict[title] = [actor] # list of actors, add that one actor to begin with       return titleActorDict """ Define the following functions to return the requested result """ def getNumFilms(titleActorDict):     res = list(titleActorDict.keys()) #listing out the data     return len(res) #returning length of list for number of films      def getLongestCastList(titleActorDict):     keys = list(titleActorDict.keys()) #listing out the data     maxCastNum = 0 #setting the maxCastNum     for key in keys: #creating a loop to iterate over the list         if(maxCastNum < len(titleActorDict[key])):              maxCastNum = len(titleActorDict[key])      return maxCastNum #returning the longest cast list      def getShortestCastList(titleActorDict):      keys = list(titleActorDict.keys())     minCastNum = 9999999 #setting the minCastNum     for key in keys:         if (minCastNum > len(titleActorDict[key])):             minCastNum = len(titleActorDict[key]) #doing something similar when getting the Longest cast list     return minCastNum def lookupActor(titleActorDict, movie, actor):     if(actor in titleActorDict[movie]): #checks if actor is within list         return True     else:         return False      def getCommonActors(titleActorDict, movie1, movie2):     resList = []     actor_list1 = titleActorDict[movie1]     actor_list2 = titleActorDict[movie2]     for actor in actor_list1:         if(actor in actor_list2):             resList.append(actor)     return resList      def getCommonActors_v2(titleActorDict, movie1, movie2, movie3):     if movie1 in titleActorDict and movie2 in titleActorDict and movie3 in titleActorDict:         actor_list1 = titleActorDict[movie1]         actor_list2 = titleActorDict[movie2]         actor_list3 = titleActorDict[movie3]         common_actors = list(set(actor_list1) & set(actor_list2) & set(actor_list3))         return common_actors     return [] def getActorMovieList(titleActorDict, actor):     movies = [movie for movie, cast_list in titleActorDict.items() if actor in cast_list]     return movies titleActorDict = make_title_dict()