<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def iter_leaf_names(self, is_leaf_fn=None):
 """Returns an iterator over the leaf names under this node."""

        for n in self.iter_leaves(is_leaf_fn=is_leaf_fn):
            yield n.name