def METHOD_NAME(self, format="bibentry"):
    """See more in :py:func:`habanero.content_negotiation`"""
    # Grouping dictionary by value :
    by_use = {}
    for doi, why in self.items():
        why_str = ", ".join(why)
        by_use[why_str] = (
            [doi] if why_str not in by_use.keys() else by_use[why_str] + [doi]
        )
    for why, dois in sorted(by_use.items()):
        msg = f"Used for {why}"
        print(msg)
        print("-" * len(msg))
        for doi in dois:
            print(self._content(doi, format=format))
        print("")