def CheckForExistence(self, filename):
    if filename:
      path = self.PathOnDMG(filename)
      return os.path.exists(path)
    else:
      return False
L{TLSMemoryBIOProtocol.getPeerCertificate} returns the
dataset/ETHPy150Open MacSysadmin/pymacadmin/utilities/diskimage_unittesting/macdmgtest.py/DMGUnitTest.CheckForExistence--crossover with--dataset/ETHPy150Open nlloyd/SubliminalCollaborator/libs/twisted/protocols/test/test_tls.py/TLSMemoryBIOTests.test_getPeerCertificate