def __init__(
        self,
        type: int,
        children: list[NL],
        context: Optional[Any] = None,
        prefix: Optional[str] = None,
        fixers_applied: Optional[list[Any]] = None,
    ) -> None:
        """
        Initializer.

        Takes a type constant (a symbol number >= 256), a sequence of
        child nodes, and an optional context keyword argument.

        As a side effect, the parent pointers of the children are updated.
        """
        assert type >= 256, type
        self.type = type
        self.children = list(children)
        for ch in self.children:
            assert ch.parent is None, repr(ch)
            ch.parent = self
        self.invalidate_sibling_maps()
        if prefix is not None:
            self.prefix = prefix
        if fixers_applied:
            self.fixers_applied = fixers_applied[:]
        else:
            self.fixers_applied = None

        Initializer.

        Takes a type constant (a symbol number >= 256), a sequence of
        child nodes, and an optional context keyword argument.

        As a side effect, the parent pointers of the children are updated.
        
src/blib2to3/pytree.py