How to use the cython.final function in Cython

@cython.returns(cython.long)
@cython.exceptval(check=True)
def ccall_except_check_always(x):
    """
    >>> ccall_except_check_always(41)
    42
    >>> ccall_except_check_always(0)
    Traceback (most recent call last):
    ValueError
    """
    if x == 0:
        raise ValueError
    return x+1


@cython.final
@cython.cclass
class CClass(object):
    """
    >>> c = CClass(2)
    >>> c.get_attr()
    int
    2
    """
    cython.declare(attr=cython.int)

    def __init__(self, attr):
        self.attr = attr

    def get_attr(self):
        print(cython.typeof(self.attr))
        return self.attr

    @cython.final
    def _visitchild(self, child, parent, attrname, idx):
        self.access_path.append((parent, attrname, idx))
        result = self._visit(child)
        self.access_path.pop()
        return result

    @cython.final
    def _visit(self, obj):
        try:
            try:
                handler_method = self.dispatch_table[type(obj)]
            except KeyError:
                handler_method = self.find_handler(obj)
                self.dispatch_table[type(obj)] = handler_method
            return handler_method(obj)
        except Errors.CompileError:
            raise
        except Errors.AbortError:
            raise
        except Exception as e:
            if DebugFlags.debug_no_exception_intercept:
                raise
            self._raise_compiler_error(obj, e)

    @cython.final
    def _visit(self, obj):
        try:
            try:
                handler_method = self.dispatch_table[type(obj)]
            except KeyError:
                handler_method = self.find_handler(obj)
                self.dispatch_table[type(obj)] = handler_method
            return handler_method(obj)
        except Errors.CompileError:
            raise
        except Errors.AbortError:
            raise
        except Exception as e:
            if DebugFlags.debug_no_exception_intercept:
                raise
            self._raise_compiler_error(obj, e)

    @cython.final
    def _visitchild(self, child, parent, attrname, idx):
        self.access_path.append((parent, attrname, idx))
        result = self._visit(child)
        self.access_path.pop()
        return result

    @cython.final
    @cython.locals(idx=int)
    def _visitchildren(self, parent, attrs):
        """
        Visits the children of the given parent. If parent is None, returns
        immediately (returning None).

        The return value is a dictionary giving the results for each
        child (mapping the attribute name to either the return value
        or a list of return values (in the case of multiple children
        in an attribute)).
        """
        if parent is None: return None
        result = {}
        for attr in parent.child_attrs:
            if attrs is not None and attr not in attrs: continue
            child = getattr(parent, attr)

    @cython.final
    @cython.locals(idx=int)
    def _visitchildren(self, parent, attrs):
        """
        Visits the children of the given parent. If parent is None, returns
        immediately (returning None).

        The return value is a dictionary giving the results for each
        child (mapping the attribute name to either the return value
        or a list of return values (in the case of multiple children
        in an attribute)).
        """
        if parent is None: return None
        result = {}
        for attr in parent.child_attrs:
            if attrs is not None and attr not in attrs: continue
            child = getattr(parent, attr)

    @cython.final
    def find_handler(self, obj):
        # to resolve, try entire hierarchy
        cls = type(obj)
        pattern = "visit_%s"
        mro = inspect.getmro(cls)
        handler_method = None
        for mro_cls in mro:
            handler_method = getattr(self, pattern % mro_cls.__name__, None)
            if handler_method is not None:
                return handler_method
        print(type(self), cls)
        if self.access_path:
            print(self.access_path)
            print(self.access_path[-1][0].pos)
            print(self.access_path[-1][0].__dict__)
        raise RuntimeError("Visitor %r does not accept object: %s" % (self, obj))

    @cython.final
    def _flatten_list(self, orig_list):
        # Flatten the list one level and remove any None
        newlist = []
        for x in orig_list:
            if x is not None:
                if type(x) is list:
                    newlist.extend(x)
                else:
                    newlist.append(x)
        return newlist

    @cython.final
    def find_handler(self, obj):
        # to resolve, try entire hierarchy
        cls = type(obj)
        pattern = "visit_%s"
        mro = inspect.getmro(cls)
        for mro_cls in mro:
            handler_method = getattr(self, pattern % mro_cls.__name__, None)
            if handler_method is not None:
                return handler_method
        print(type(self), cls)
        if self.access_path:
            print(self.access_path)
            print(self.access_path[-1][0].pos)
            print(self.access_path[-1][0].__dict__)
        raise RuntimeError("Visitor %r does not accept object: %s" % (self, obj))