input: Write a function called `add_marks` which takes two parameters: `marks` (a list) and `mark` (an integer). The function should add the `mark` to each value in the `marks` 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([1, 2, 3], -1) == [0, 1, 2]
  assert add_marks([78, 89, 90, 91], 12) == [90, 101, 102, 103]
output: def add_marks(marks, mark):
      return [x + mark for x in marks]