docs: public static INDArray[] principalComponents(INDArray cov) {
          Preconditions.checkArgument(cov.isMatrix() && cov.isSquare(), "Convariance matrix must be a square matrix: has shape %s", cov.shape());
          INDArray[] result = new INDArray[2];
          result[0] = Nd4j.eye(cov.rows());
          result[1] = Eigen.symmetricGeneralizedEigenvalues(result[0], cov, true);
          return result;
      }