input: Write a function to add a specified mark to each value in a given list of marks. The function should take two parameters: marks (a list) and mark (an integer). If the list is empty, return an empty list.
  assert add_marks([87, 56, 99, 54], 4) == [91, 60, 103, 58]
  assert add_marks([], 4) == []
  assert add_marks([10, 20, 30], 5) == [15, 25, 35]
  assert add_marks([75, 80], 0) == [75, 80]
output: def add_marks(marks, mark):
      if not marks:
          return []
      return [x + mark for x in marks]