code: def GetChangeAddress(self, from_addr=None):
          
          if from_addr is not None:
              for contract in self._contracts.values():
                  if contract.ScriptHash == from_addr:
                      return contract.ScriptHash
  
          for contract in self._contracts.values():
              if contract.IsStandard:
                  return contract.ScriptHash
  
          if len(self._contracts.values()):
              for k, v in self._contracts.items():
                  return v
  
          raise Exception("Could not find change address")
docs: Get the address where change is send to.
  
          Args:
              from_address (UInt160): (optional) from address script hash.
  
          Raises:
              Exception: if change address could not be found.
  
          Returns:
              UInt160: script hash.