def get_citation_by_reference(self, type: str, reference: str) -> Optional[Citation]:
        """Get a citation object by its type and reference."""
        citation_hash = hash_citation(type=type, reference=reference)
        return self.get_citation_by_hash(citation_hash)
def get_citation_by_reference ( self , type : str , reference : str ) -> Optional [ Citation ] : citation_hash = hash_citation ( type = type , reference = reference ) return self . get_citation_by_hash ( citation_hash )
Get a citation object by its type and reference.