def CheckForExistence(self, filename):
    if filename:
      path = self.PathOnDMG(filename)
      return os.path.exists(path)
    else:
      return False
Make sure filename doesn't exist on the tested image.
dataset/ETHPy150Open MacSysadmin/pymacadmin/utilities/diskimage_unittesting/macdmgtest.py/DMGUnitTest.CheckForExistence