Visitor Class — langchain Architecture

Source Code

libs/core/langchain_core/structured_query.py lines 15–68

class Visitor(ABC):
    """Defines interface for IR translation using a visitor pattern."""

    allowed_comparators: Sequence[Comparator] | None = None
    """Allowed comparators for the visitor."""

    allowed_operators: Sequence[Operator] | None = None
    """Allowed operators for the visitor."""

    def _validate_func(self, func: Operator | Comparator) -> None:
        if (
            isinstance(func, Operator)
            and self.allowed_operators is not None
            and func not in self.allowed_operators
        ):
            msg = (
                f"Received disallowed operator {func}. Allowed "
                f"comparators are {self.allowed_operators}"
            )
            raise ValueError(msg)
        if (
            isinstance(func, Comparator)
            and self.allowed_comparators is not None
            and func not in self.allowed_comparators
        ):
            msg = (
                f"Received disallowed comparator {func}. Allowed "
                f"comparators are {self.allowed_comparators}"
            )
            raise ValueError(msg)

    @abstractmethod
    def visit_operation(self, operation: Operation) -> Any:
        """Translate an Operation.

        Args:
            operation: Operation to translate.
        """

    @abstractmethod
    def visit_comparison(self, comparison: Comparison) -> Any:
        """Translate a Comparison.

        Args:
            comparison: Comparison to translate.
        """

    @abstractmethod
    def visit_structured_query(self, structured_query: StructuredQuery) -> Any:
        """Translate a StructuredQuery.

        Args:
            structured_query: StructuredQuery to translate.
        """