[Question] How to filter str with vertex in K-neighbor API (POST Version)

### Feature Description (功能描述)

如何根据节点字符串类型属性筛选节点，例如city属性为Hongkong
请求内容设置如下后
"label": "person",
"properties": {
"city": "P.eq('Hongkong')"
}
报错：
{
"exception": "class org.apache.hugegraph.HugeException",
"message": "Invalid value ''Hongkong'', expect a number",
"cause": "org.apache.hugegraph.HugeException: Can't read json: Unexpected character (''' (code 39)): expected a valid value (JSON String, Number, Array, Object or token 'null', 'true' or 'false')\n at [Source: (String)\"'Hongkong'\"; line: 1, column: 2]"
}
此外尝试了"city": "P.eq(\"Hongkong\")" 还有 "city": "P.eq(Hongkong)"，均无法筛选节点并报错