docs: public Collection<HFCAIdentity> getHFCAIdentities(User registrar) throws IdentityException, InvalidArgumentException {
          if (registrar == null) {
              throw new InvalidArgumentException("Registrar should be a valid member");
          }
  
          logger.debug(format("identity  url: %s, registrar: %s", url, registrar.getName()));
  
          try {
              JsonObject result = httpGet(HFCAIdentity.HFCA_IDENTITY, registrar);
  
              Collection<HFCAIdentity> allIdentities = new ArrayList<>();
  
              JsonArray identities = result.getJsonArray("identities");
              if (identities != null && !identities.isEmpty()) {
                  for (int i = 0; i < identities.size(); i++) {
                      JsonObject identity = identities.getJsonObject(i);
                      HFCAIdentity idObj = new HFCAIdentity(identity);
                      allIdentities.add(idObj);
                  }
              }
  
              logger.debug(format("identity  url: %s, registrar: %s done.", url, registrar));
              return allIdentities;
          } catch (HTTPException e) {
              String msg = format("[HTTP Status Code: %d] - Error while getting all users from url '%s': %s", e.getStatusCode(), url, e.getMessage());
              IdentityException identityException = new IdentityException(msg, e);
              logger.error(msg);
              throw identityException;
          } catch (Exception e) {
              String msg = format("Error while getting all users from url '%s': %s", url, e.getMessage());
              IdentityException identityException = new IdentityException(msg, e);
              logger.error(msg);
              throw identityException;
          }
  
      }