docstr: Credentials - Encrypted Credentials - Is Encrypted
docstr_tok: ["Credentials","-","Encrypted","Credentials","-","Is","Encrypted"]
code: def test_is_encrypted(self):
      """Credentials - Encrypted Credentials - Is Encrypted"""
      assert_true(self._credentials.is_encrypted())
  
imports: import json
  import os
  from collections import OrderedDict
  from botocore.exceptions import ClientError
  from mock import patch, MagicMock
  from moto import mock_kms, mock_ssm
  from nose.tools import assert_equal, assert_false, assert_is_instance, assert_is_none, assert_is_not_none, assert_not_equal, assert_true
  from streamalert.alert_processor.outputs.output_base import OutputProperty
  from streamalert.alert_processor.outputs.credentials.provider import SSMDriver, LocalFileDriver, Credentials, OutputCredentialsProvider, EphemeralUnencryptedDriver, SpooledTempfileDriver, get_formatted_output_credentials_name
  from tests.unit.streamalert.alert_processor import PREFIX, CONFIG, KMS_ALIAS, REGION, MOCK_ENV
  from tests.unit.streamalert.alert_processor.helpers import encrypt_with_kms, setup_mock_kms
label_desc: Use image node_id 3 for calling the TestCredentialsEncrypted obj's underlying member method code with example usage: obj.test_is_encrypted() without return types