I have a dto class which describes an object of kcell telephony API
Something like:

/**
 * ...
 * */
export class KcellEventRequest {
    /**
     * ...
     * */
    cmd: 'event'

    /**
     * ...
     * */
    crm_token: string
...
}

for every kcell event

When I receive data, I use serializer and got object of KcellEventRequest class

private serializer (body: any): KcellEventRequest | KcellHistoryRequest | KcellContactRequest | KcellRatingRequest {
    body.authorization = this.parseToken(body.crm_token)
    switch (body.cmd) {
        case 'event' :
            return plainToInstance(KcellEventRequest, body)
        case 'history':
            return plainToInstance(KcellHistoryRequest, body)
        case 'contact':
            return plainToInstance(KcellContactRequest, body)
        case 'rating':
            return plainToInstance(KcellRatingRequest, body)
        default:
            throw Error('Incorrect cmd')
    }
}

async handleRequest (body: any, headers: any): Promise<any> {
        // serialize object
    const callObject = this.serializer(body)
        // {{read next}}
    return await callObject.handle(headers)
}

Each class (KcellEventRequest | KcellHistoryRequest | KcellContactRequest | KcellRatingRequest) implements TelephonyAPIHandler with method handle
This method triggers my app to do something

I don’t like the handler function being in the dto, but it simplifies my logic here
return await callObject.handle(headers)

How do I separate the handler function from the dto?