routeRules help

Can someone help me with this:

routeRules: { 
        '/chat/:chat_id': { proxy: '/api/v1/:chat_id/public' },
    },

routeRules: { 
        '/chat/:chat_id': { proxy: '/api/v1/:chat_id/public' },
    },

routeRules: { 
        '/chat/:chat_id': { proxy: '/api/v1/:chat_id/public' },
    },

routeRules: { 
        '/chat/:chat_id': { proxy: '/api/v1/:chat_id/public' },
    },

it doesn't work and I can't find any documentation anywhere