public INDArray sigmoidDerivative(INDArray x, INDArray wrt) {
    NDValidation.validateNumerical("sigmoidDerivative", "x", x);
    NDValidation.validateNumerical("sigmoidDerivative", "wrt", wrt);
    return Nd4j.exec(new org.nd4j.linalg.api.ops.impl.transforms.gradient.SigmoidDerivative(x, wrt))[0];
  }