docstr: Test PyBytes_AsString()
docstr_tok: ["Test","PyBytes_AsString","(",")"]
code: def test_asstring(self):
      """Test PyBytes_AsString()"""
      asstring = _testcapi.bytes_asstring
  
      self.assertEqual(asstring(b"abc", 4), b"abc\0")
      self.assertEqual(asstring(b"abc\0def", 8), b"abc\0def\0")
      self.assertRaises(TypeError, asstring, "abc", 0)
      self.assertRaises(TypeError, asstring, object(), 0)
  
imports: import unittest
  from test.support import import_helper
  from _testcapi import PY_SSIZE_T_MIN, PY_SSIZE_T_MAX
label_desc: Use image node_id 7 for calling the CAPITest obj's underlying member method code with example usage: obj.test_asstring() without return types