code: public static INDArray convn(INDArray input, INDArray kernel, Type type, int[] axes) {
          return Nd4j.getConvolution().convn(input, kernel, type, axes);
      }
docs: ND Convolution
  
  @param input  the input to op
  @param kernel the kerrnel to op with
  @param type   the opType of convolution
  @param axes   the axes to do the convolution along
  @return the convolution of the given input and kernel