since(cond, _id) {
        let id = this._tsid(_id, `since()`)
        if (cond && cond.__id__) cond = cond[0]
        let s = this.ts(undefined, id)
        s[0] = cond ? 0 : s[1] + 1
        return s
    }
Candles since the event occured (cond === true)
@param {(boolean|TS)} cond - the condition