code: def testLessThan1K(self):
      self.assertEqual(upload_tracker.readable_bytes_string(42), "42 B")
  
imports: import sys
  from unittest import mock
  from tensorboard import test
  from tensorboard.uploader import upload_tracker
label_desc: Use image node_id 2 for calling the ReadableBytesStringTest obj's underlying member method code with example usage: obj.testLessThan1K() without return types