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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 connect_to_ec2(region='us-east-1', access_key=None, secret_key=None):
 """ Connect to AWS ec2 :type region: str :param region: AWS region to connect to :type access_key: str :param access_key: AWS access key id :type secret_key: str :param secret_key: AWS secret access key :returns: boto.ec2.connection.EC2Connection -- EC2 connection """


    if access_key:
        # Connect using supplied credentials
        logger.info('Connecting to AWS EC2 in {}'.format(region))
        connection = ec2.connect_to_region(
            region,
            aws_access_key_id=access_key,
            aws_secret_access_key=secret_key)
    else:
        # Fetch instance metadata
        metadata = get_instance_metadata(timeout=1, num_retries=1)
        if metadata:
            try:
                region = metadata['placement']['availability-zone'][:-1]
            except KeyError:
                pass

        # Connect using env vars or boto credentials
        logger.info('Connecting to AWS EC2 in {}'.format(region))
        connection = ec2.connect_to_region(region)

    if not connection:
        logger.error('An error occurred when connecting to EC2')
        sys.exit(1)

    return connection