boto3 : AttributeError: 'EC2' object has no attribute 'create_instances'

Question

client = boto3.client('ec2', 
        aws_access_key_id=key,
        aws_secret_access_key=secret,
        region_name='ap-southeast-1')


    response = client.create_instances(
        DryRun=True,
        ImageId=ami1,
        MinCount=1,
        MaxCount=1,
        KeyName='my-key',
        SecurityGroupIds=[sg1, sg2],
        InstanceType='m3.medium',
        Placement={
            'AvailabilityZone': 'ap-southeast-1a'
        },
        SubnetId=sb1,
        NetworkInterfaces=[
            {
                'NetworkInterfaceId': vpc1,
                'SubnetId': sb1,
                'Description': 'Description'
            }
        ]
    )
    print response 

getting error while making api call to create instance, I have verified other operation like describe_images is working fine so keys are proper.

am I missing something ?