.

publish/src/rdf/ontology.rs

@@ -295,7 +295,7 @@ WHERE {{
             .collect()
     }
 
-    pub fn datatypes(&self) -> impl Iterator<Item = NamedNode> {
+    pub fn datatypes(&self) -> BTreeSet<NamedNode> {
         self.store
             .quads_for_pattern(
                 None,
@@ -307,7 +307,7 @@ WHERE {{
             .filter_map(|quad| match quad.subject {
                 NamedOrBlankNode::NamedNode(subject) => Some(subject),
                 _ => None,
-            })
+            }).collect()
     }
 
     pub fn is_read_only<'a>(&self, triple: impl Into<TripleRef<'a>>) -> bool {