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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 _parse(self, date_str, format='%Y-%m-%d'):
 """ helper function for parsing FRED date string into datetime """

        rv = pd.to_datetime(date_str, format=format)
        if hasattr(rv, 'to_pydatetime'):
            rv = rv.to_pydatetime()
        return rv