Add count() method on SingleTypeRelationships

Author: vnickolov

applications/algorithms/machinery/src/main/java/org/neo4j/gds/applications/algorithms/machinery/MutateRelationshipService.java

@@ -69,6 +69,6 @@ public RelationshipsWritten mutate(
 
         graphStore.addRelationshipType(singleTypeRelationships);
 
-        return new RelationshipsWritten(singleTypeRelationships.topology().elementCount());
+        return new RelationshipsWritten(singleTypeRelationships.count());
     }
 }

core-api/src/main/java/org/neo4j/gds/core/loading/SingleTypeRelationships.java

@@ -52,6 +52,10 @@ public interface SingleTypeRelationships {
 
     Optional<RelationshipPropertyStore> inverseProperties();
 
+    default long count() {
+        return topology().elementCount();
+    }
+
     /**
      * Filters the relationships to include only the given property if present.
      */