How to handle both Upper and Lower case for Xpath assertions in Readyapi

Is there is a Function in groovy script to handle both lower case and uppercase 

The below function is for upper case

${="${Run TestCase_Create Client Setup#AddressLine1_PHYS}".toUpperCase()}

The below function is for lower case

${="${Run TestCase_Create Client Setup#AddressLine1_PHYS}".toLowerCase()}

Similarly i want a function to manage both upper and lower case.