input: Write a python function to calculate the sum, mean, and median of a dataset.
  ```python
  def calculate_statistics(dataset):
      s = sum(dataset)
      mean = s / len(dataset)
      
      dataset_sorted = sorted(dataset)
      m_m = len(dataset_sorted)
      
      if m_m % 2 == 0:
          m1 = dataset_sorted[m_m // 2 - 1]
          m2 = dataset_sorted[m_m // 2]
          median = (m1 + m2) / 2
      else:
          median = dataset_sorted[m_m // 2]
      
      return s, mean, median
  
  assert calculate_statistics([1, 5, 8, 9, 12, 17, 20]) == (72, 10.285714285714286, 9)
  assert calculate_statistics([1, 2, 3, 4, 5, 6]) == (21, 3.5, 3.5)
  assert calculate_statistics([10, 20, 30, 40, 50]) == (150, 30.0, 30)
output: def calculate_statistics(dataset):
      s = sum(dataset)
      mean = s / len(dataset)
      
      dataset_sorted = sorted(dataset)
      m_m = len(dataset_sorted)
      
      if m_m % 2 == 0:
          m1 = dataset_sorted[m_m // 2 - 1]
          m2 = dataset_sorted[m_m // 2]
          median = (m1 + m2) / 2
      else:
          median = dataset_sorted[m_m // 2]
      
      return s, mean, median
  
  assert calculate_statistics([1, 5, 8, 9, 12, 17, 20]) == (72, 10.285714285714286, 9)
  assert calculate_statistics([1, 2, 3, 4, 5, 6]) == (21, 3.5, 3.5)
  assert calculate_statistics([10, 20, 30, 40, 50]) == (150, 30.0, 30)