code: def signMsg(self,
                  msg: Dict,
                  identifier: Identifier=None,
                  otherIdentifier: Identifier=None):
          
          idr = self.requiredIdr(idr=identifier or otherIdentifier)
          signer = self._signerById(idr)
          signature = signer.sign(msg)
          return signature
docs: Creates signature for message using specified signer
  
          :param msg: message to sign
          :param identifier: signer identifier
          :param otherIdentifier:
          :return: signature that then can be assigned to request