code: public static INDArray conv2d(INDArray input, INDArray kernel, Type type) {
          return Nd4j.getConvolution().conv2d(input, kernel, type);
      }
docs: 2d convolution (aka the last 2 dimensions
  
  @param input  the input to op
  @param kernel the kernel to convolve with
  @param type
  @return