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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 authorization_link(self, redirect_uri):
        '''Construct OAuth2 authorization link.

        Params:    redirect_uri -> URI for receiving callback with token
        Returns authorization URL as string
        '''
        args = '?client_id=%s&redirect_uri=%s' % (
            self.app_key,
            redirect_uri
        )
        uri = "/".join([BASE_URL, API_VERSION, OAUTH, args])
        return uri