code: def AddToBalance(self, assetId, fixed8_val):
          
          found = False
          for key, balance in self.Balances.items():
              if key == assetId:
                  self.Balances[assetId] = self.Balances[assetId] + fixed8_val
                  found = True
          if not found:
              self.Balances[assetId] = fixed8_val
docs: Add amount to the specified balance.
  
          Args:
              assetId (UInt256):
              fixed8_val (Fixed8): amount to add.