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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 login(self, username=None, password=None, token=None, two_factor_callback=None):
 """Logs the user into GitHub for protected API calls. :param str username: login name :param str password: password for the login :param str token: OAuth token :param func two_factor_callback: (optional), function you implement to provide the Two Factor Authentication code to GitHub when necessary """

        if username and password:
            self._session.basic_auth(username, password)
        elif token:
            self._session.token_auth(token)

        # The Session method handles None for free.
        self._session.two_factor_auth_callback(two_factor_callback)