docs: public static void saveSparseCSV(FMatrixSparseTriplet A , String fileName )
              throws IOException
      {
          PrintStream fileStream = new PrintStream(fileName);
  
          fileStream.println(A.getNumRows() + " " + A.getNumCols() +" "+A.nz_length+ " real");
          for (int i = 0; i < A.nz_length; i++) {
              int row = A.nz_rowcol.data[i*2];
              int col = A.nz_rowcol.data[i*2+1];
              float value = A.nz_value.data[i];
  
              fileStream.println(row+" "+col+" "+value);
          }
          fileStream.close();
      }