code: def testReadinto(self):
      # verify readinto
      self.f.write(b"12")
      self.f.close()
      a = array("b", b"x" * 10)
      self.f = self.open(TESTFN, "rb")
      n = self.f.readinto(a)
      self.assertEqual(b"12", a.tobytes()[:n])
  
imports: import sys
  import os
  import unittest
  from array import array
  from weakref import proxy
  import io
  import _pyio
  from test.support import gc_collect
  from test.support.os_helper import TESTFN
  from test.support import os_helper
  from test.support import warnings_helper
  from collections import UserList
label_desc: Use image node_id 5 for calling the AutoFileTests obj's underlying member method code with example usage: obj.testReadinto() without return types