input: Write a function to add a specified integer 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 marks 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([100, 100, 100], 0)==[100, 100, 100]
  assert add_marks([30, 40, 50], -10)==[20, 30, 40]
output: def add_marks(marks, mark):
      if not marks:
          return []
      return [x + mark for x in marks]