Who_meets prereqs (passed_rosters, desired_prereqs) : Description: There exist certain classes that are restricted by one or more prerequisites, or classes that you must pass before you can enroll in the restricted class. The Registrar knows who has passed certain courses, and they know the sequence of prerequisites that must be met, but they are having a hard time figuring out who actually meets these prerequisites. Determine the set of students who meet the given prerequisite criteria. Parameters: passed_rosters, a dictionary of sets as described above (only this time, this structure represents the students who have passed a particular course). desired_prereqs, a list of strings that described the prerequisites that must all be met. desired_prereqs will contain one of two possible string types. A single course name means that the student must have passed that course. Two course names with an "OR" in between means that the student must have passed at least one of those two courses. A student must meet each of the individual criteria in this list in order to be included in the result. Return value: a set containing the names of all students who meet the prerequisite criteria Examples: refer to the last page. check_prereqs (rosters, passed rosters, all prereqs): Description: The Registrar needs to verify that everyone enrolled in courses for next semester are allowed to be enrolled for those courses based on each course's list of prerequisites. Build and return a dictionary of course & student set pairs to report on each student who was enrolled in a course but did not meet the prereqs for that course. If no student is incorrectly enrolled in a course, this dictionary should be empty. You can assume that if someone meets the prereqs for one course, then will satisfy the prereqs for all all those prereqs, so on and on so forth. In other words, if course X requires course Y, and course Y has its own prereqs A, B, and C, you don't need to ensure that everyone in course X has passed A, B, and C. You only need to check that the students in course X have all passed course Y. Parameters: rosters, a dictionary of sets as described above. passed_rosters, a dictionary of sets as described above (this time, its passed classes instead). all_prereqs, a dictionary of lists of prerequisite strings as seen in the who_meets_prereqs function. Return value: a dictionary of courses (keys) and sets of student names who are enrolled but did not meet the prereqs for that course (values) [could be empty!] Examples: refer to the last page.