def savedJSONInvariants(testCase, savedJSON):
    """
    Assert a few things about the result of L{eventAsJSON}, then return it.

    @param testCase: The L{TestCase} with which to perform the assertions.
    @type testCase: L{TestCase}

    @param savedJSON: The result of L{eventAsJSON}.
    @type savedJSON: L{unicode} (we hope)

    @return: C{savedJSON}
    @rtype: L{unicode}

    @raise AssertionError: If any of the preconditions fail.
    """
    testCase.assertIsInstance(savedJSON, unicode)
    testCase.assertEqual(savedJSON.count("\n"), 0)
    return savedJSON

    Assert a few things about the result of L{eventAsJSON}, then return it.

    @param testCase: The L{TestCase} with which to perform the assertions.
    @type testCase: L{TestCase}

    @param savedJSON: The result of L{eventAsJSON}.
    @type savedJSON: L{unicode} (we hope)

    @return: C{savedJSON}
    @rtype: L{unicode}

    @raise AssertionError: If any of the preconditions fail.
    
stackoverflow/venv/lib/python3.6/site-packages/twisted/logger/test/test_json.py