//Assuming that the name of the test step is "Test Request", and modify as needed
def request = context.expand('${Test Request#Request}')
log.info request
If you already have testStep object(based on your existing code snippet) and do not like to use as above, then you may use as below
def tempRequestObject = "\${${testStep.name}#Request}"
def request = context.expand(tempRequestObject)
log.info request
Similarly, you may get the response too.
def tempReponseObject = "\${${testStep.name}#Response}"
def response = context.expand(tempResponseObject)
log.info response