docs: public ListVpcsResponse listVpcs(ListVpcsRequest request) {
          checkNotNull(request, "request should not be null.");
          InternalRequest internalRequest = this.createRequest(request, HttpMethodName.GET, VPC_PREFIX);
          if (request.getMarker() != null) {
              internalRequest.addParameter("marker", request.getMarker());
          }
          if (request.getMaxKeys() > 0) {
              internalRequest.addParameter("maxKeys", String.valueOf(request.getMaxKeys()));
          }
          if (request.getIsDefault() != null) {
              internalRequest.addParameter("isDefault", request.getIsDefault().toString());
          }
          return invokeHttpClient(internalRequest, ListVpcsResponse.class);
      }