code: def addSigningInformation(self, account, permission):
          
          self.constructTx()
          self["blockchain"] = self.blockchain.rpc.chain_params
  
          if isinstance(account, self.publickey_class):
              self["missing_signatures"] = [str(account)]
          else:
              accountObj = self.account_class(account)
              authority = accountObj[permission]
              # We add a required_authorities to be able to identify
              # how to sign later. This is an array, because we
              # may later want to allow multiple operations per tx
              self.update({"required_authorities": {accountObj["name"]: authority}})
              for account_auth in authority["account_auths"]:
                  account_auth_account = self.account_class(account_auth[0])
                  self["required_authorities"].update(
                      {account_auth[0]: account_auth_account.get(permission)}
                  )
  
              # Try to resolve required signatures for offline signing
              self["missing_signatures"] = [x[0] for x in authority["key_auths"]]
              # Add one recursion of keys from account_auths:
              for account_auth in authority["account_auths"]:
                  account_auth_account = self.account_class(account_auth[0])
                  self["missing_signatures"].extend(
                      [x[0] for x in account_auth_account[permission]["key_auths"]]
                  )
docs: This is a private method that adds side information to a
              unsigned/partial transaction in order to simplify later
              signing (e.g. for multisig or coldstorage)
  
              FIXME: Does not work with owner keys!