input: from typing import List
  
  class MedianFinder:
   """A class to find the median of an unsorted list of numbers.
   Examples:
   >>> mf = MedianFinder()
   >>> mf.add(5)
   >>> mf.add(3)
   >>> mf.add(4)
   >>> mf.find_median()
   4
   >>> mf.add(1)
   >>> mf.add(2)
   >>> mf.find_median()
   3
   """
   def __init__(self):
       self._data = []
   
   def add(self, num):
       self._data.append(num)
   
   def find_median(self):
       data = sorted(self._data)
       n = len(data)
       return (data[(n-1)//2] + data[n//2])/2
output:     
      def __init__(self):
          self._data = []
      
      def add(self, num):
          self._data.append(num)
      
      def find_median(self):
          data = sorted(self._data)
          n = len(data)
          return (data[(n-1)//2] + data[n//2])/2
  