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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 variables(self):
 """All variables in the connected data source"""

        url = self.base_url + 'ts'
        headers = {'Authorization': 'Bearer {}'.format(self.auth())}
        r = requests.get(url, headers=headers)
        df = pd.read_json(r.content, orient='records')
        return pd.Series(df['variable'].unique(), name='variable')