Given a tree rooted at
n
, the visitor has the option of
overriding all traversal of the children of
n
. If no
changes were made to
n
and the visitor wishes to prevent
further traversal of the tree, then it should return
n
. If
changes were made to the subtree, then the visitor should return a
copy of
n
with appropriate changes. Finally, if the
visitor does not wish to override traversal of the subtree rooted at
n
, then it should return
null
.
This method is typically called by the method
override(parent, n)
. If a subclass overrides the
method override(parent, n)
then this method
may not be called.