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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 get_lambda_arn(app, account, region):
 """Get lambda ARN. Args: account (str):
 AWS account name. region (str):
 Region name, e.g. us-east-1 app (str):
 Lambda function name Returns: str: ARN for requested lambda function """

    session = boto3.Session(profile_name=account, region_name=region)
    lambda_client = session.client('lambda')

    lambda_arn = None
    paginator = lambda_client.get_paginator('list_functions')

    for lambda_functions in paginator.paginate():
        for lambda_function in lambda_functions['Functions']:
            if lambda_function['FunctionName'] == app:
                lambda_arn = lambda_function['FunctionArn']
                LOG.debug("Lambda ARN for lambda function %s is %s.", app, lambda_arn)
                break
        if lambda_arn:
            break

    if not lambda_arn:
        LOG.fatal('Lambda function with name %s not found in %s %s', app, account, region)
        raise LambdaFunctionDoesNotExist(
            'Lambda function with name {0} not found in {1} {2}'.format(app, account, region))

    return lambda_arn