langchain/document_loaders/duckdb_loader.py/DuckDBLoader/__init__
class DuckDBLoader:    def __init__(
        self,
        query: str,
        database: str = ":memory:",
        read_only: bool = False,
        config: Optional[Dict[str, str]] = None,
        page_content_columns: Optional[List[str]] = None,
        metadata_columns: Optional[List[str]] = None,
    ):
        self.query = query
        self.database = database
        self.read_only = read_only
        self.config = config or {}
        self.page_content_columns = page_content_columns
        self.metadata_columns = metadata_columns