docs: public static boolean isSymmetric( DMatrixSparseCSC A , double tol ) {
          if( A.numRows != A.numCols )
              return false;
  
          int N = A.numCols;
  
          for (int i = 0; i < N; i++) {
              int idx0 = A.col_idx[i];
              int idx1 = A.col_idx[i+1];
  
              for (int index = idx0; index < idx1; index++) {
                  int j = A.nz_rows[index];
                  double value_ji = A.nz_values[index];
                  double value_ij = A.get(i,j);
  
                  if( Math.abs(value_ij-value_ji) > tol )
                      return false;
              }
          }
  
          return true;
      }