docs: @Override
      public DMatrixRMaj getUpper(DMatrixRMaj upper )
      {
          int numRows = LU.numRows < LU.numCols ? LU.numRows : LU.numCols;
          int numCols = LU.numCols;
  
          upper = UtilDecompositons_DDRM.checkZerosLT(upper,numRows,numCols);
  
          for( int i = 0; i < numRows; i++ ) {
              for( int j = i; j < numCols; j++ ) {
                  upper.unsafe_set(i,j, LU.unsafe_get(i,j));
              }
          }
  
          return upper;
      }