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