code: public Observable<ComapiResult<MessageSentResponse>> sendMessage(@NonNull final String conversationId, @NonNull final MessageToSend message) {
  
          final String token = getToken();
  
          if (sessionController.isCreatingSession()) {
              return getTaskQueue().queueSendMessage(conversationId, message);
          } else if (TextUtils.isEmpty(token)) {
              return Observable.error(getSessionStateErrorDescription());
          } else {
              return doSendMessage(token, conversationId, message);
          }
      }
docs: Send message to the chanel.
  
  @param conversationId ID of a conversation to send a message to.
  @param message        Message to be send.
  @return Observable to send message to a conversation.