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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 bibtex(self):
 """Return a BiBTeX entry for the current article."""

        warnings.warn("bibtex should be queried with ads.ExportQuery(); You will "
                      "hit API ratelimits very quickly otherwise.", UserWarning)
        return ExportQuery(bibcodes=self.bibcode, format="bibtex").execute()