Add Student

Create a function named add_student that takes three arguments: name (string), age (integer), and courses (a list of strings). The function should:

1. Check if the student name already exists in the student_records dictionary. If it does, print "Student '<name>' already exists.".
2. If the name does not exist, add it to student_records with age, an empty set for grades (this model assumes each grade value is unique), and a set of courses.
3. Print "Student '<name>' added successfully.".

Add the following block of code at the bottom of your code:

add_student("Alice", 20, ["Math", "Physics"])
add_student("Bob", 22, ["Biology", "Chemistry"])
print(student_records)