code: def GetStandardAddress(self):
          
          for contract in self._contracts.values():
              if contract.IsStandard:
                  return contract.ScriptHash
  
          raise Exception("Could not find a standard contract address")
docs: Get the Wallet's default address.
  
          Raises:
              Exception: if no default contract address is set.
  
          Returns:
              UInt160: script hash.