The TES example package contains a Lambda function that, when run,
will attempt to retrieve AWS credentials. The goal of TES is to allow
users to retrieve credentials without having them hard-coded on the
system itself. 

Assuming no credentials exist on the system, when the Lambda function 
is run, temporary credentials will be sourced from the cloud. They 
will be formatted as <Access Key, Secret Key, Session Key, Expiration Date>.

The code sample performs logger initialization and credential retrieval
is outside of the function handler. This means that a pinned lambda 
should be used to test functionality. 

In case you would like to use an On-Demand Lambda function, you will then 
need to create a subscription to invoke the Lambda function
(so that the handler is executed).

### SETUP ###
1. In order to use this example, you will need to include greengrasssdk, boto3, 
botocore and any of the dependencies those libraries require in the zip file before
uploading it.

2. After creating a zip file, create a Lambda function
in the Lambda Console.

    Handler: lambda_function.lambda_handler
    Runtime: python2.7
    Timeout: 3s
    Role: any basic execution role can be used here

3. Create a group that contains your Greengrass Core and the Lambda 
function you've just created.

4. Deploy the latest Greengrass release to your device.

5. Ensure that your logging configuration includes either a logging 
configuration for CW, the FileSystem, or both. For example:

    "Logging": {
            "Content": [
                {
                    "Type": "FileSystem",
                    "Component": "GreengrassSystem",
                    "Level": "DEBUG",
                    "Space": 25600
                },
                {
                    "Type": "FileSystem",
                    "Component": "Lambda",
                    "Level": "DEBUG",
                    "Space": 25600
                },
                {
                    "Type": "AWSCloudWatch",
                    "Component": "Lambda",
                    "Level": "DEBUG"
                },
                {
                    "Type": "AWSCloudWatch",
                    "Component": "GreengrassSystem",
                    "Level": "DEBUG"
                }
            ]
        }

6. Make a deployment to your Greengrass Core, then start your Greengrass
Core. The core will check for any new deployments and will proceed to 
download the newest configuration file (group.json) as well as the Lambda
function you've created. 

7. Check either the local logs or  CloudWatch logs for output from the function.

    Local Path: /greengrass/var/log/user/<REGION>/<ACCOUNT>/<FUNCTION_NAME>.log
    CloudWatch: /aws/greengrass/Lambda/<REGION>/<ACCOUNT>/<FUNCTION_NAME>