input: Write a python function to generate a sequence of numbers from start to end.
  assert generate_sequence(3, 15) == [3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15]
  assert generate_sequence(1, 5) == [1, 2, 3, 4, 5]
  assert generate_sequence(-3, 3) == [-3, -2, -1, 0, 1, 2, 3]
output: def generate_sequence(start, end):
      return list(range(start, end + 1))