_calcOutputShape(inputShapes) {
    let shape1 = inputShapes[0].slice()
    let shape2 = inputShapes[1].slice()
    shape1.splice(this.dotAxes[0], 1)
    shape2.splice(this.dotAxes[1], 1)
    this.outputShape = shape1.concat(shape2)
    if (this.outputShape.length === 1) {
      this.outputShape.push(1)
    }
  }
Calculate output shape

@param {number[][]} inputShapes