def retrieve_review(self, reviewer, product):
        """Retrieve review that the given reviewer put the given product.

        Args:
          reviewer: An instance of Reviewer.
          product: An instance of Product.

        Returns:
          A review object.

        Raises:
          TypeError: when given reviewer and product aren't instance of
            specified reviewer and product class when this graph is constructed.
          KeyError: When the reviewer does not review the product.
        """
        if not isinstance(reviewer, self._reviewer_cls):
            raise TypeError(
                "Type of given reviewer isn't acceptable:", reviewer,
                ", expected:", self._reviewer_cls)
        elif not isinstance(product, self._product_cls):
            raise TypeError(
                "Type of given product isn't acceptable:", product,
                ", expected:", self._product_cls)

        try:
            return self.graph[reviewer][product]["review"]
        except TypeError:
            raise KeyError(
                "{0} does not review {1}.".format(reviewer, product))
def retrieve_review ( self , reviewer , product ) : if not isinstance ( reviewer , self . _reviewer_cls ) : raise TypeError ( "Type of given reviewer isn't acceptable:" , reviewer , ", expected:" , self . _reviewer_cls ) elif not isinstance ( product , self . _product_cls ) : raise TypeError ( "Type of given product isn't acceptable:" , product , ", expected:" , self . _product_cls ) try : return self . graph [ reviewer ] [ product ] [ "review" ] except TypeError : raise KeyError ( "{0} does not review {1}." . format ( reviewer , product ) )
Retrieve review that the given reviewer put the given product.

        Args:
          reviewer: An instance of Reviewer.
          product: An instance of Product.

        Returns:
          A review object.

        Raises:
          TypeError: when given reviewer and product aren't instance of
            specified reviewer and product class when this graph is constructed.
          KeyError: When the reviewer does not review the product.