class_docstr: Credentials Class Unittest class.
docstr: Test Credentials.save().
code: def test_Credentials_save(self):
      """Test Credentials.save()."""
      c = Credentials.get_current()
      c.activation = _Activation("some_email", True)
      truth = textwrap.dedent(
          """
              [general]
              email = "some_email"
          """
      ).lstrip()
  
      streamlit_root_path = os.path.join(
          "/mock/home/folder", file_util.CONFIG_FOLDER_NAME
      )
  
      # patch streamlit.*.os.makedirs instead of os.makedirs for py35 compat
      with patch(
          "streamlit.runtime.credentials.open", mock_open(), create=True
      ) as open, patch(
          "streamlit.runtime.credentials.os.makedirs"
      ) as make_dirs:
          c.save()
  
          make_dirs.assert_called_once_with(
              streamlit_root_path, exist_ok=True
          )
          open.return_value.write.assert_called_once_with(truth)
  
imports: import os
  import textwrap
  import unittest
  from pathlib import Path
  from unittest.mock import MagicMock, call, mock_open, patch
  import pytest
  import requests_mock
  from testfixtures import tempdir
  from streamlit import file_util
  from streamlit.runtime.credentials import Credentials, _Activation, _verify_email, email_prompt
label_desc: Use image node_id 14 for calling the CredentialsClassTest obj's underlying member method code with example usage: obj.test_Credentials_save() without return types