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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def load_cert_chain(self, certfile, keyfile=None):
 """Load a private key and the corresponding certificate. The certfile string must be the path to a single file in PEM format containing the certificate as well as any number of CA certificates needed to establish the certificate's authenticity. The keyfile string, if present, must point to a file containing the private key. Otherwise the private key will be taken from certfile as well. """

        self._certfile = certfile
        self._keyfile = keyfile