def modify_hsm(HsmArn=None, SubnetId=None, EniIp=None, IamRoleArn=None,
    ExternalId=None, SyslogIp=None):
    """
    Modifies an HSM.
    See also: AWS API Documentation
    
    
    :example: response = client.modify_hsm(
        HsmArn='string',
        SubnetId='string',
        EniIp='string',
        IamRoleArn='string',
        ExternalId='string',
        SyslogIp='string'
    )
    
    
    :type HsmArn: string
    :param HsmArn: [REQUIRED]
            The ARN of the HSM to modify.
            

    :type SubnetId: string
    :param SubnetId: The new identifier of the subnet that the HSM is in. The new subnet must be in the same Availability Zone as the current subnet.

    :type EniIp: string
    :param EniIp: The new IP address for the elastic network interface (ENI) attached to the HSM.
            If the HSM is moved to a different subnet, and an IP address is not specified, an IP address will be randomly chosen from the CIDR range of the new subnet.
            

    :type IamRoleArn: string
    :param IamRoleArn: The new IAM role ARN.

    :type ExternalId: string
    :param ExternalId: The new external ID.

    :type SyslogIp: string
    :param SyslogIp: The new IP address for the syslog monitoring server. The AWS CloudHSM service only supports one syslog monitoring server.

    :rtype: dict
    :return: {
        'HsmArn': 'string'
    }
    
    
    """
    pass
