input: Write a python function to retrieve student information by ID.
  assert get_student_info(123456) == ("Alice", "alice@example.com", "123-456-789")
  assert get_student_info(789456) == ("Bob", "bob@example.com", "456-789-012")
  assert get_student_info(111111) == None
output: def get_student_info(student_id):
      students = {
          123456: ("Alice", "alice@example.com", "123-456-789"),
          789456: ("Bob", "bob@example.com", "456-789-012")
      }
      return students.get(student_id, None)