diff --git a/lib/instance-set.js b/lib/instance-set.js
index d426ea2..953c5a5 100644
--- a/lib/instance-set.js
+++ b/lib/instance-set.js
@@ -36,14 +36,14 @@ class InstanceSet {
     for (let inst of this.set) {
       let match = true;
       for (let k in instance) {
-	if (inst[k] !== instance[k]) {
-	  match = false;
-	  break;
-	}
+        if (inst[k] !== instance[k]) {
+          match = false;
+          break;
+        }
       }
 
       if (match)
-	res.push(inst);
+        res.push(inst);
     }
 
     res.sort(function(a, b) {
@@ -51,20 +51,20 @@ class InstanceSet {
       let keysB = Object.keys(b);
 
       if (keysA.length != keysB.length)
-	return keysB.length - keysA.length;
+        return keysB.length - keysA.length;
 
       keysA.sort();
       keysB.sort();
 
       for (let i = 0; i < keysA.length; ++ i) {
-	if (keysA[i] > keysB[i])
-	  return 1;
-	else if (keysA[i] < keysB[i])
-	  return -1;
-	else if (a[keysA[i]] > b[keysB[i]])
-	  return 1;
-	else if (a[keysA[i]] < b[keysB[i]])
-	  return -1;
+        if (keysA[i] > keysB[i])
+          return 1;
+        else if (keysA[i] < keysB[i])
+          return -1;
+        else if (a[keysA[i]] > b[keysB[i]])
+          return 1;
+        else if (a[keysA[i]] < b[keysB[i]])
+          return -1;
       }
 
       return 0;
@@ -75,18 +75,18 @@ class InstanceSet {
 
   subset(instance) {
     let res = [];
-    
+
     for (let inst of this.set) {
       let match = true;
       for (let k in inst) {
-	if (inst[k] !== instance[k]) {
-	  match = false;
-	  break;
-	}
+        if (inst[k] !== instance[k]) {
+          match = false;
+          break;
+        }
       }
 
       if (match)
-	res.push(inst);
+        res.push(inst);
     }
 
     res.sort(function(a, b) {
@@ -94,31 +94,35 @@ class InstanceSet {
       let keysB = Object.keys(b);
 
       if (keysA.length != keysB.length)
-	return keysA.length - keysB.length;
+        return keysA.length - keysB.length;
 
       keysA.sort();
       keysB.sort();
 
       for (let i = 0; i < keysA.length; ++ i) {
-	if (keysA[i] > keysB[i])
-	  return 1;
-	else if (keysA[i] < keysB[i])
-	  return -1;
-	else if (a[keysA[i]] > b[keysB[i]])
-	  return 1;
-	else if (a[keysA[i]] < b[keysB[i]])
-	  return -1;
+        if (keysA[i] > keysB[i])
+          return 1;
+        else if (keysA[i] < keysB[i])
+          return -1;
+        else if (a[keysA[i]] > b[keysB[i]])
+          return 1;
+        else if (a[keysA[i]] < b[keysB[i]])
+          return -1;
       }
 
       return 0;
     });
 
-    return res;    
+    return res;
   }
 
   forEach(callback) {
     return this.set.forEach(callback);
   }
+
+  values() {
+    return this.set.values();
+  }
 }
 
 module.exports = InstanceSet;