def get_closest_leaf(self, topology_only=False, is_leaf_fn=None):
min_node, min_dist, max_node, max_dist = self._get_farthest_and_closest_leaves(<EOL>topology_only=topology_only, is_leaf_fn=is_leaf_fn)<EOL>return min_node, min_dist<EOL>
Returns node's closest descendant leaf and the distance to
        it.

        :argument False topology_only: If set to True, distance
          between nodes will be referred to the number of nodes
          between them. In other words, topological distance will be
          used instead of branch length distances.

        :return: A tuple containing the closest leaf referred to the
          current node and the distance to it.