cross(src1, src2, _id) {
        let id = this._tsid(_id, `cross`)
        let x = (src1[0] > src2[0]) !== (src1[1] > src2[1])
        return this.ts(x, id, src1.__tf__)
    }
When one time-series crosses another
@param {TS} src1 - TS1
@param {TS} src2 - TS2
@return {TS} - New time-series