code: def test_uses_stdin_as_default_input(self, mock_input):
      mock_input.readline.return_value = "input_string"
      getpass._raw_input(stream=StringIO())
      mock_input.readline.assert_called_once_with()
  
imports: import getpass
  import os
  import unittest
  from io import BytesIO, StringIO, TextIOWrapper
  from unittest import mock
  from test import support
label_desc: Use image node_id 3 for calling the GetpassRawinputTest obj's underlying member method code with example usage: obj.test_uses_stdin_as_default_input(mock_input) without return types