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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_partition_name(cls, region=None):
 """ Gets the name of the partition given the region name. If region name is not provided, this method will use Boto3 to get name of the region where this code is running. This implementation is borrowed from AWS CLI https://github.com/aws/aws-cli/blob/1.11.139/awscli/customizations/emr/createdefaultroles.py#L59 :param region: Optional name of the region :return: Partition name """


        if region is None:
            # Use Boto3 to get the region where code is running. This uses Boto's regular region resolution
            # mechanism, starting from AWS_DEFAULT_REGION environment variable.
            region = boto3.session.Session().region_name

        region_string = region.lower()
        if region_string.startswith("cn-"):
            return "aws-cn"
        elif region_string.startswith("us-gov"):
            return "aws-us-gov"
        else:
            return "aws"