input: Write a python function to calculate the median of a list of numbers.
  assert median([1, 3, 3, 6, 7, 8, 9]) == 6
  assert median([1, 2, 3, 4, 5, 6, 8, 9]) == 4.5
  assert median([10, 20, 30, 40, 50]) == 30
  assert median([1, 2, 3]) == 2
output: def median(numbers):
      sorted_numbers = sorted(numbers)
      n = len(sorted_numbers)
      mid = n // 2
  
      if n % 2 == 0:
          return (sorted_numbers[mid - 1] + sorted_numbers[mid]) / 2
      else:
          return sorted_numbers[mid]