diff --git a/src/internals/insert.rs b/src/internals/insert.rs
index 53e41075..be2f3325 100644
--- a/src/internals/insert.rs
+++ b/src/internals/insert.rs
@@ -220,7 +220,13 @@ pub trait ComponentSource: ArchetypeSource {
 
 /// A collection with a known length.
 pub trait KnownLength {
+    /// Gets the length of the collection.
     fn len(&self) -> usize;
+
+    /// Returns true only if the collection is empty.
+    fn is_empty(&self) -> bool {
+        self.len() == 0
+    }
 }
 
 /// Converts a type into a [`ComponentSource`].
diff --git a/src/internals/permissions.rs b/src/internals/permissions.rs
index cbd65fa5..ba4da312 100644
--- a/src/internals/permissions.rs
+++ b/src/internals/permissions.rs
@@ -265,11 +265,10 @@ impl<T: PartialEq> Default for Permissions<T> {
 impl<T: PartialEq + Debug> Debug for Permissions<T> {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         fn list<V: Debug>(items: &[V]) -> String {
-            use itertools::Itertools;
             items
                 .iter()
                 .map(|x| format!("{:?}", x))
-                .fold1(|x, y| format!("{}, {}", x, y))
+                .reduce(|x, y| format!("{}, {}", x, y))
                 .unwrap_or_else(|| "".to_owned())
         }
 
@@ -285,11 +284,10 @@ impl<T: PartialEq + Debug> Debug for Permissions<T> {
 impl<T: PartialEq + Display> Display for Permissions<T> {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         fn list<V: Display>(items: &[V]) -> String {
-            use itertools::Itertools;
             items
                 .iter()
                 .map(|x| format!("{}", x))
-                .fold1(|x, y| format!("{}, {}", x, y))
+                .reduce(|x, y| format!("{}, {}", x, y))
                 .unwrap_or_else(|| "".to_owned())
         }
 
diff --git a/src/storage.rs b/src/storage.rs
index 3a5dcfb8..474efb1f 100644
--- a/src/storage.rs
+++ b/src/storage.rs
@@ -81,7 +81,7 @@ pub use crate::internals::{
     hash::{ComponentTypeIdHasher, U64Hasher},
     insert::{
         ArchetypeSource, ArchetypeWriter, ComponentSource, ComponentWriter, IntoComponentSource,
-        IntoSoa, UnknownComponentWriter,
+        IntoSoa, KnownLength, UnknownComponentWriter,
     },
     storage::{
         archetype::{Archetype, ArchetypeIndex, EntityLayout},