AWS lambda which stops EC2 instances with Env Dev tag

lambda_stop.py

import boto3

# Enter the region your instances are in. Include only the region without specifying Availability Zone; e.g., 'us-east-1'
region = 'eu-west-1'

filters = [{'Name':'tag:Env', 'Values':['Dev']}]

def lambda_handler(event, context):
    ec2 = boto3.client('ec2', region_name=region)

    instances = [instance.id for instance in boto3.resource('ec2').instances.filter(Filters=filters)]
    ec2.stop_instances(InstanceIds=instances)
    print 'stopped your instances: ' + str(instances)

    """
    ec2.start_instances(InstanceIds=instances)
    print 'started your instances: ' + str(instances)
    """

if __name__ == "__main__":
    lambda_handler({},None)

policy.json

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Sid": "VisualEditor0",
            "Effect": "Allow",
            "Action": [
                "logs:CreateLogStream",
                "logs:PutLogEvents"
            ],
            "Resource": "arn:aws:logs:*:*:*"
        },
        {
            "Sid": "VisualEditor1",
            "Effect": "Allow",
            "Action": [
                "ec2:DescribeInstances",
                "ec2:Start*",
                "ec2:Stop*"
            ],
            "Resource": "*"
        },
        {
            "Sid": "VisualEditor2",
            "Effect": "Allow",
            "Action": "logs:CreateLogGroup",
            "Resource": "arn:aws:logs:*:*:*"
        }
    ]
}