code: def decryptMsg(self, ciphertext, textMsg=True):
          
  
          if not self.sessionStore.containsSession(self.recipientId, self.deviceId):
              raise NoSessionException("No session for: %s, %s" % (self.recipientId, self.deviceId))
  
          sessionRecord = self.sessionStore.loadSession(self.recipientId, self.deviceId)
          plaintext = self.decryptWithSessionRecord(sessionRecord, ciphertext)
  
          self.sessionStore.storeSession(self.recipientId, self.deviceId, sessionRecord)
  
          return plaintext
docs: :type ciphertext: WhisperMessage
          :type textMsg: Bool set this to False if you are decrypting bytes
                         instead of string