diff --git a/neurom/io/utils.py b/neurom/io/utils.py
index <HASH>..<HASH> 100644
--- a/neurom/io/utils.py
+++ b/neurom/io/utils.py
@@ -38,6 +38,7 @@ from . import load_data
 from . import check
 from neurom.utils import memoize
 import os
+from collections import deque
 
 
 @memoize
rabase changes

Revert "removed collections"

This reverts commit 1e1f<I>da3bbc2bb0c9bd<I>ec<I>b9be<I>c.

minor change

segment radial dists test

moved the specialized iterator inside the _impl feature

segment radial dists test

moved the specialized iterator inside the _impl feature