Method constructor

proxy/model-proxy.js:41–47

(onUsage)

 */
class UsageNormalizer extends Transform {
    constructor(onUsage) {
        super();
        this._buf = '';
        this._onUsage = onUsage;
        this._inputTokens = 0;
        this._outputTokens = 0;
    }

    _transform(chunk, _enc, cb) {
        this._buf += chunk.toString();