Converts the given resource to bytes representation in the encoding
        specified by :param:`encoding` and returns it.

def to_bytes(self, obj, encoding=None):
        """
        Converts the given resource to bytes representation in the encoding
        specified by :param:`encoding` and returns it.
        """
        if encoding is None:
            encoding = self.encoding
        text = self.to_string(obj)
        return bytes_(text, encoding=self.encoding)