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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 _read_credential_file(self, cfg):
 """ Parses the credential file with Rackspace-specific labels. """

        self.username = cfg.get("rackspace_cloud", "username")
        try:
            self.password = cfg.get("rackspace_cloud", "api_key", raw=True)
        except ConfigParser.NoOptionError as e:
            # Allow either the use of either 'api_key' or 'password'.
            self.password = cfg.get("rackspace_cloud", "password", raw=True)