input: Write a python function to find students with grades above 80.
  assert find_top_students({"James": 95, "Alice": 80, "John": 75}) == ["James"]
  assert find_top_students({"James": 95, "Alice": 85, "John": 90}) == ["James", "Alice", "John"]
  assert find_top_students({"James": 70, "Alice": 65, "John": 75}) == []
output: def find_top_students(grades):
      return [student for student, grade in grades.items() if grade > 80]