public function add(string $name, string $credential, string $address, string $proofMaterial = null)
    {
        return $this->httpPostJson('wxa/addnearbypoi', [
            'related_name' => $name,
            'related_credential' => $credential,
            'related_address' => $address,
            'related_proof_material' => $proofMaterial,
        ]);
    }