Check if value exists into object.

        :param pointer: the path to search in
        :param expected: the expected value
        :param raise_onerror: should raise on error?
        :return: boolean

def check(self, pointer, expected, raise_onerror=False):
        """Check if value exists into object.

        :param pointer: the path to search in
        :param expected: the expected value
        :param raise_onerror: should raise on error?
        :return: boolean
        """
        obj = self.document
        for token in Pointer(pointer):
            try:
                obj = token.extract(obj, bypass_ref=True)
            except ExtractError as error:
                if raise_onerror:
                    raise Error(*error.args)
                logger.exception(error)
                return False
        return obj == expected