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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 fetch_token(self, code, state):
 """ Fetch the token, using the verification code. Also, make sure the state received in the response matches the one in the request. Returns the access_token. """

        if self.state != state:
            raise MismatchingStateError()
        self.token = self.oauth.fetch_token(
            '%saccess_token/' % OAUTH_URL, code=code,
            client_secret=self.client_secret)
        return self.token['access_token']