code: public Observable<ComapiResult<Void>> addParticipants(@NonNull final String conversationId, @NonNull final List<Participant> participants) {
  
          final String token = getToken();
  
          if (sessionController.isCreatingSession()) {
              return getTaskQueue().queueAddParticipants(conversationId, participants);
          } else if (TextUtils.isEmpty(token)) {
              return Observable.error(getSessionStateErrorDescription());
          } else {
              return doAddParticipants(token, conversationId, participants);
          }
      }
docs: Returns observable to add a list of participants to a conversation.
  
  @param conversationId ID of a conversation to update.
  @param participants   New conversation participants details.
  @return Observable to add participants to a conversation.