old_contents: 
  import os
  
  TESTS_RESOURCE_LOCATION = "${TESTS_RESOURCE_LOCATION}"
  
  def file_contents(file_name):
  
      with open(os.path.join(TESTS_RESOURCE_LOCATION, file_name)) as f:
          lines = f.read()
  
      return lines
  
new_contents: 
  import os
  
  TESTS_RESOURCE_LOCATION = "${TESTS_RESOURCE_LOCATION}"
  
  def file_contents(file_name):
  
      with open(os.path.join(TESTS_RESOURCE_LOCATION, file_name)) as f:
          content = f.read()
  
      return content
  
subject: Change name of variable in file_contents.