input: Write a function to find the second largest number in a list.
  assert second_largest([1, 2, 3, 4, 5]) == 4
  assert second_largest([10, 20, 30, 40, 50]) == 40
  assert second_largest([5, 5, 5, 4, 4, 3]) == 4
output: def second_largest(numbers):
      unique_numbers = list(set(numbers))
      unique_numbers.sort(reverse=True)
      return unique_numbers[1] if len(unique_numbers) > 1 else None