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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 authenticate(self, request, **kwargs):
 """Authenticates a user based on the OIDC code flow."""


        self.request = request
        if not self.request:
            return None

        state = self.request.GET.get('state')
        code = self.request.GET.get('code')
        nonce = kwargs.pop('nonce', None)

        if not code or not state:
            return None

        reverse_url = self.get_settings('OIDC_AUTHENTICATION_CALLBACK_URL',
                                        'oidc_authentication_callback')

        token_payload = {
            'client_id': self.OIDC_RP_CLIENT_ID,
            'client_secret': self.OIDC_RP_CLIENT_SECRET,
            'grant_type': 'authorization_code',
            'code': code,
            'redirect_uri': absolutify(
                self.request,
                reverse(reverse_url)
            ),
        }

        # Get the token
        token_info = self.get_token(token_payload)
        id_token = token_info.get('id_token')
        access_token = token_info.get('access_token')

        # Validate the token
        payload = self.verify_token(id_token, nonce=nonce)

        if payload:
            self.store_tokens(access_token, id_token)
            try:
                return self.get_or_create_user(access_token, id_token, payload)
            except SuspiciousOperation as exc:
                LOGGER.warning('failed to get or create user: %s', exc)
                return None

        return None