AWS Secrets manager-SDK using python

Hi I am trying to retrieve secrets using python SDK which will retrieve the secret name called test in the specified region's AWS secrets manager and getting the below error while running a simple python script:

#!/usr/bin/env python
import boto3
import base64
from botocore.exceptions import ClientError

def get_secret():

    secret_name = "test"
    region_name = "tesdas"
    print("inside rds secrete")
    # Create a Secrets Manager client
    session = boto3.session.Session()
    client = session.client(
        service_name='secretsmanager',
        region_name=region_name
    )

    # In this sample we only handle the specific exceptions for the 'GetSecretValue' API.
    # See https://docs.aws.amazon.com/secretsmanager/latest/apireference/API_GetSecretValue.html
    # We rethrow the exception by default.

    try:
        get_secret_value_response = client.get_secret_value(
            SecretId=secret_name
        )
        # Decrypts secret using the associated KMS CMK.
        # Depending on whether the secret is a string or binary, one of these fields will be populated.
        if 'SecretString' in get_secret_value_response:
            secret = get_secret_value_response['SecretString']
            print("RDS Secret")
            print(secret)
        else:
            decoded_binary_secret = base64.b64decode(get_secret_value_response['SecretBinary'])

get_secret()

Below is the error which I am getting, while executing the script:

Traceback (most recent call last):
  File "test.py", line 60, in <module>
    get_secret()
  File "test.py", line 18, in get_secret
    region_name=region_name
  File "/usr/lib/python2.7/site-packages/boto3/session.py", line 263, in client
    aws_session_token=aws_session_token, config=config)
  File "/usr/lib/python2.7/site-packages/botocore/session.py", line 836, in create_client
    client_config=config, api_version=api_version)
  File "/usr/lib/python2.7/site-packages/botocore/client.py", line 64, in create_client
    service_model = self._load_service_model(service_name, api_version)
  File "/usr/lib/python2.7/site-packages/botocore/client.py", line 97, in _load_service_model
    api_version=api_version)
  File "/usr/lib/python2.7/site-packages/botocore/loaders.py", line 132, in _wrapper
    data = func(self, *args, **kwargs)
  File "/usr/lib/python2.7/site-packages/botocore/loaders.py", line 378, in load_service_model
    known_service_names=', '.join(sorted(known_services)))
botocore.exceptions.UnknownServiceError: Unknown service: 'secretsmanager'. Valid service names are: acm, apigateway, application-autoscaling, appstream, athena, autoscaling, batch, budgets, clouddirectory, cloudformation, cloudfront, cloudhsm, cloudsearch, cloudsearchdomain, cloudtrail, cloudwatch, codebuild, codecommit, codedeploy, codepipeline, codestar, cognito-identity, cognito-idp, cognito-sync, config, cur, datapipeline, dax, devicefarm, directconnect, discovery, dms, ds, dynamodb, dynamodbstreams, ec2, ecr, ecs, efs, elasticache, elasticbeanstalk, elastictranscoder, elb, elbv2, emr, es, events, firehose, gamelift, glacier, greengrass, health, iam, importexport, inspector, iot, iot-data, kinesis, kinesisanalytics, kms, lambda, lex-models, lex-runtime, lightsail, logs, machinelearning, marketplace-entitlement, marketplacecommerceanalytics, meteringmarketplace, mturk, opsworks, opsworkscm, organizations, pinpoint, polly, rds, redshift, rekognition, resourcegroupstaggingapi, route53, route53domains, s3, sdb, servicecatalog, ses, shield, sms, snowball, sns, sqs, ssm, stepfunctions, storagegateway, sts, support, swf, waf, waf-regional, workdocs, workspaces, xray