code: private Collection<User> getSFSRecipients() {
          List<User> answer = new ArrayList<>();
          for(String recipient : recipients) {
              User sfsUser = CommandUtil.getSfsUser(recipient, api);
              if(sfsUser != null)
                  answer.add(sfsUser);
          }
          return answer;
      }
docs: Get list of smartfox users (recipients)
  
  @return list of smartfox users