code: def _compute_expect_frac(self, num_sessions):
      if num_sessions > 200000:
          return 10000.0 / num_sessions
      elif num_sessions >= 200:
          return 0.95
      elif num_sessions >= 50:
          return 0.9
      return 1
  
imports: from __future__ import print_function
  from __future__ import division
  from __future__ import absolute_import
  import unittest
  import turicreate
  import random
  import tempfile
  import math
  import numpy
  from numbers import Number
  from .None import util
  import pytest
  from turicreate.toolkits._internal_utils import _mac_ver
  from turicreate.toolkits._main import ToolkitError
  import uuid
label_desc: Use image node_id 2 for calling the ActivityClassifierAutoValdSetTest obj's underlying member method code with example usage: obj._compute_expect_frac(num_sessions) and returns: int, unknown, int, int