input: Write a python function to find the second largest number in a list.
  assert second_largest([10, 20, 4, 45, 99]) == 45
  assert second_largest([5, 8, 12, 7, 3]) == 8
  assert second_largest([12, 15, 11, 20, 19]) == 19
output: def second_largest(numbers):
      unique_numbers = list(set(numbers))
      unique_numbers.sort()
      return unique_numbers[-2]