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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def create_sns_event(app_name, env, region, rules):
 """Create SNS lambda event from rules. Args: app_name (str):
 name of the lambda function env (str):
 Environment/Account for lambda function region (str):
 AWS region of the lambda function rules (str):
 Trigger rules from the settings """

    session = boto3.Session(profile_name=env, region_name=region)
    sns_client = session.client('sns')

    topic_name = rules.get('topic')
    lambda_alias_arn = get_lambda_alias_arn(app=app_name, account=env, region=region)
    topic_arn = get_sns_topic_arn(topic_name=topic_name, account=env, region=region)
    protocol = 'lambda'

    statement_id = '{}_sns_{}'.format(app_name, topic_name)
    principal = 'sns.amazonaws.com'
    add_lambda_permissions(
        function=lambda_alias_arn,
        statement_id=statement_id,
        action='lambda:InvokeFunction',
        principal=principal,
        source_arn=topic_arn,
        env=env,
        region=region)

    sns_client.subscribe(TopicArn=topic_arn, Protocol=protocol, Endpoint=lambda_alias_arn)
    LOG.debug("SNS Lambda event created")

    LOG.info("Created SNS event subscription on topic %s", topic_name)