code: public FutureData<TokenList> listTokens(String identity, int page, int perPage) {
          if (identity == null) {
              throw new IllegalArgumentException("An identity is required");
          }
          FutureData<TokenList> future = new FutureData<>();
          ParamBuilder b = newParams();
          if (page > 0) {
              b.put("page", page);
          }
          if (perPage > 0) {
              b.put("per_page", perPage);
          }
          URI uri = b.forURL(config.newAPIEndpointURI(IDENTITY + "/" + identity + "/token"));
          Request request = config.http().
                  GET(uri, new PageReader(newRequestCallback(future, new TokenList(), config)));
          performRequest(future, request);
          return future;
      }
docs: /*
  List tokens associated with an identity
  
  @param identity which identity you want to list the tokens of
  @param page     page number (can be 0)
  @param perPage  items per page (can be 0)
  @return List of identities