code: @Override
      public void invert( ZMatrixRMaj inv ) {
          if( inv.numRows != n || inv.numCols != n ) {
              throw new RuntimeException("Unexpected matrix dimension");
          }
          if( inv.data == t ) {
              throw new IllegalArgumentException("Passing in the same matrix that was decomposed.");
          }
  
          if(decomposer.isLower()) {
              setToInverseL(inv.data);
          } else {
              throw new RuntimeException("Implement");
          }
      }
docs: Sets the matrix 'inv' equal to the inverse of the matrix that was decomposed.
  
  @param inv Where the value of the inverse will be stored.  Modified.