langchain/document_loaders/bigquery.py/BigQueryLoader/__init__
class BigQueryLoader:    def __init__(
        self,
        query: str,
        project: Optional[str] = None,
        page_content_columns: Optional[List[str]] = None,
        metadata_columns: Optional[List[str]] = None,
    ):
        self.query = query
        self.project = project
        self.page_content_columns = page_content_columns
        self.metadata_columns = metadata_columns