langchain/utilities/bibtex.py/BibtexparserWrapper/validate_environment
class BibtexparserWrapper:    def validate_environment(cls, values: Dict) -> Dict:
        """Validate that the python package exists in environment."""
        try:
            import bibtexparser  # noqa
        except ImportError:
            raise ImportError(
                "Could not import bibtexparser python package. "
                "Please install it with `pip install bibtexparser`."
            )

        return values