old_contents: def saddle_points():
      pass
  
new_contents: def saddle_points(m):
      mt = transpose(m)
      if not m == transpose(mt):
          raise ValueError
      return set((i, j) for i, row in enumerate(m) for j, col in enumerate(mt)
                  if (row[j] == min(row) and col[i] == max(col))
                  or (row[j] == max(row) and col[i] == min(col)))
  
  
  def transpose(m):
      return [list(col) for col in zip(*m)]
  
subject: Add initial solution