code: def _help_product_norm_fast(self, A, B):
      # for profiling
      t = 2
      itmax = 5
      D = MatrixProductOperator(A, B)
      est, v, w, nmults, nresamples = _onenormest_core(D, D.T, t, itmax)
      return est
  
imports: from __future__ import division, print_function, absolute_import
  import numpy
  from numpy.testing import assert_allclose, assert_equal, assert_
  import pytest
  import scipy.linalg
  import scipy.sparse.linalg
  from scipy.sparse.linalg._onenormest import _onenormest_core, _algorithm_2_2
label_desc: Use image node_id 6 for calling the TestOnenormest obj's underlying member method code with example usage: obj._help_product_norm_fast(A, B) and returns: est