value = COMPARATOR_TO_BER[func]
        return f"{value}"
[docs]    def visit_operation(self, operation: Operation) -> str:
        if operation.operator in UNARY_OPERATORS and len(operation.arguments) == 1:
            operator = self._format_func(operation.operator)
            return operator + "(" + operation.arguments[0].accept(self) + ")"
        elif operation.operator in UNARY_OPERATORS:
            raise ValueError(
                f'"{operation.operator.value}" can have only one argument in Milvus'
            )
        else:
            args = [arg.accept(self) for arg in operation.arguments]
            operator = self._format_func(operation.operator)
            return "(" + (" " + operator + " ").join(args) + ")"
[docs]    def visit_comparison(self, comparison: Comparison) -> str:
        comparator = self._format_func(comparison.comparator)
        processed_value = process_value(comparison.value)
        attribute = comparison.attribute
        return "( " + attribute + " " + comparator + " " + processed_value + " )"
[docs]    def visit_structured_query(
        self, structured_query: StructuredQuery
    ) -> Tuple[str, dict]:
        if structured_query.filter is None:
            kwargs = {}
        else:
            kwargs = {"expr": structured_query.filter.accept(self)}
        return structured_query.query, kwargs