code: @Override
      public T execute() {
          try {
              return getHttpClient().executeWithRetries(this);
          } catch (InvalidStateException e) {
              Optional<ApiError> conflictError = Iterables.tryFind(e.getErrors(), CONFLICT_ERROR);
              if (conflictError.isPresent()) {
                  String id = conflictError.get().getLinks().get("conflicting_resource_id");
                  return handleConflict(getHttpClient(), id).execute();
              } else {
                  throw Throwables.propagate(e);
              }
          }
      }
docs: Executes this request.
  
  Returns the response entity.
  
  @throws com.gocardless.GoCardlessException