diff --git a/python/extension/src/algorithms.rs b/python/extension/src/algorithms.rs
index 195e1fcb..c141468e 100644
--- a/python/extension/src/algorithms.rs
+++ b/python/extension/src/algorithms.rs
@@ -1,4 +1,4 @@
-use ltp::{drop_get_entities, eisner, viterbi_decode_postprocessing};
+use ltp::utils::{drop_get_entities, eisner, viterbi_decode_postprocessing};
 use pyo3::prelude::*;
 
 /// Convert Tags to Entities
diff --git a/python/extension/src/hook.rs b/python/extension/src/hook.rs
index 620640ab..9c8c24d0 100644
--- a/python/extension/src/hook.rs
+++ b/python/extension/src/hook.rs
@@ -1,4 +1,4 @@
-use ltp::hook::Hook;
+use ltp::utils::hook::Hook;
 use pyo3::prelude::*;
 
 #[pyclass(module = "ltp_extension.algorithms", name = "Hook", subclass)]
diff --git a/python/extension/src/stnsplit.rs b/python/extension/src/stnsplit.rs
index 8babd0a6..5b933577 100644
--- a/python/extension/src/stnsplit.rs
+++ b/python/extension/src/stnsplit.rs
@@ -1,4 +1,4 @@
-use ltp::{stn_split_with_options, SplitOptions};
+use ltp::utils::{stn_split_with_options, SplitOptions};
 use pyo3::prelude::*;
 use pyo3::types::{PyList, PyString};
 use rayon::prelude::*;
diff --git a/rust/ltp-cffi/src/stnsplit.rs b/rust/ltp-cffi/src/stnsplit.rs
index 7a29bff7..74195f2a 100644
--- a/rust/ltp-cffi/src/stnsplit.rs
+++ b/rust/ltp-cffi/src/stnsplit.rs
@@ -1,5 +1,5 @@
 use crate::Callback;
-use ltp::stnsplit::{
+use ltp::utils::stnsplit::{
     stn_split as r_stn_split, stn_split_with_options as r_stn_split_with_options, SplitOptions,
 };
 use std::slice;
diff --git a/rust/ltp/src/lib.rs b/rust/ltp/src/lib.rs
index d4da425b..a43f2989 100644
--- a/rust/ltp/src/lib.rs
+++ b/rust/ltp/src/lib.rs
@@ -1,9 +1,5 @@
-pub mod eisner;
-pub mod entities;
-pub mod hook;
 pub mod perceptron;
-pub mod stnsplit;
-pub mod viterbi;
+pub mod utils;
 
 pub use perceptron::{
     Algorithm, CWSDefinition, NERDefinition, POSDefinition, PaMode, Perceptron, Trainer,
@@ -18,7 +14,4 @@ pub type POSModel = SerdePOSModel;
 #[cfg(feature = "serialization")]
 pub type NERModel = SerdeNERModel;
 
-pub use eisner::eisner;
-pub use entities::{drop_get_entities, get_entities};
-pub use stnsplit::{stn_split, stn_split_with_options, SplitOptions};
-pub use viterbi::viterbi_decode_postprocessing;
+
diff --git a/rust/ltp/src/perceptron/definition/mod.rs b/rust/ltp/src/perceptron/definition/mod.rs
index 85965ec2..bbe94e84 100644
--- a/rust/ltp/src/perceptron/definition/mod.rs
+++ b/rust/ltp/src/perceptron/definition/mod.rs
@@ -7,7 +7,7 @@ use std::collections::HashSet;
 use std::fmt::Debug;
 use std::io::Read;
 
-use crate::get_entities;
+use crate::utils::get_entities;
 use crate::perceptron::Sample;
 pub use cws::CWSDefinition;
 pub use ner::NERDefinition;
diff --git a/rust/ltp/src/perceptron/model.rs b/rust/ltp/src/perceptron/model.rs
index 2af857a8..14bb853e 100644
--- a/rust/ltp/src/perceptron/model.rs
+++ b/rust/ltp/src/perceptron/model.rs
@@ -259,7 +259,7 @@ impl<Feature, ParamStorage, Param> Perceptron<NERDefinition, Feature, ParamStora
     }
 }
 
-use crate::{get_entities, CWSDefinition, NERDefinition, POSDefinition};
+use crate::{utils::get_entities, CWSDefinition, NERDefinition, POSDefinition};
 
 impl<Feature, ParamStorage, Param> Perceptron<CWSDefinition, Feature, ParamStorage, Param>
     where
diff --git a/rust/ltp/src/eisner.rs b/rust/ltp/src/utils/eisner.rs
similarity index 100%
rename from rust/ltp/src/eisner.rs
rename to rust/ltp/src/utils/eisner.rs
diff --git a/rust/ltp/src/entities.rs b/rust/ltp/src/utils/entities.rs
similarity index 100%
rename from rust/ltp/src/entities.rs
rename to rust/ltp/src/utils/entities.rs
diff --git a/rust/ltp/src/hook.rs b/rust/ltp/src/utils/hook.rs
similarity index 99%
rename from rust/ltp/src/hook.rs
rename to rust/ltp/src/utils/hook.rs
index c8d9e783..a533310d 100644
--- a/rust/ltp/src/hook.rs
+++ b/rust/ltp/src/utils/hook.rs
@@ -378,7 +378,7 @@ mod tests {
     }
 
     #[test]
-    fn test_dag() {
+    fn test_dag() -> Result<()> {
         let mut dag = Dag::with_size_hint(5);
         let mut ans: Vec<Vec<usize>> = vec![Vec::new(); 5];
         for i in 0..=3 {
@@ -394,8 +394,10 @@ mod tests {
         assert_eq!(dag.size_hint_for_iterator, 4);
 
         for i in 0..=3 {
-            let edges: Vec<usize> = dag.iter_edges(i).collect();
+            let edges: Vec<usize> = dag.iter_edges(i)?.collect();
             assert_eq!(ans[i], edges);
         }
+
+        Ok(())
     }
 }
diff --git a/rust/ltp/src/utils/mod.rs b/rust/ltp/src/utils/mod.rs
new file mode 100644
index 00000000..e9bd4920
--- /dev/null
+++ b/rust/ltp/src/utils/mod.rs
@@ -0,0 +1,10 @@
+pub mod eisner;
+pub mod entities;
+pub mod hook;
+pub mod stnsplit;
+pub mod viterbi;
+
+pub use eisner::eisner;
+pub use entities::{drop_get_entities, get_entities};
+pub use stnsplit::{stn_split, stn_split_with_options, SplitOptions};
+pub use viterbi::viterbi_decode_postprocessing;
\ No newline at end of file
diff --git a/rust/ltp/src/stnsplit.rs b/rust/ltp/src/utils/stnsplit.rs
similarity index 100%
rename from rust/ltp/src/stnsplit.rs
rename to rust/ltp/src/utils/stnsplit.rs
diff --git a/rust/ltp/src/viterbi.rs b/rust/ltp/src/utils/viterbi.rs
similarity index 100%
rename from rust/ltp/src/viterbi.rs
rename to rust/ltp/src/utils/viterbi.rs