new_contents: '''
  Implement a MapSum class with insert, and sum methods.
  
  For the method insert, you'll be given a pair of (string, integer). The string represents the key and the integer represents the value. If the key already existed, then the original key-value pair will be overridden to the new one.
  
  For the method sum, you'll be given a string representing the prefix, and you need to return the sum of all the pairs' value whose key starts with the prefix.
  '''
  
  
  class MapSum:
  
      def __init__(self):
          """
          Initialize your data structure here.
          """
          self.theMap = {}
          
  
      def insert(self, key, val):
          """
          :type key: str
          :type val: int
          :rtype: void
          """
          self.theMap[key] = val;
          
  
      def sum(self, prefix):
          """
          :type prefix: str
          :rtype: int
          """
          sum = 0; 
          for i in self.theMap.keys():
              if i.startswith(prefix):
                  sum += self.theMap[i]
          return sum
  
  
  # Your MapSum object will be instantiated and called as such:
  # obj = MapSum()
  # obj.insert(key,val)
  # param_2 = obj.sum(prefix)
  
subject: Create 677-Map-Sum-Pairs.py