diff --git a/filterApis.js b/filterApis.js
new file mode 100644
index 0000000..084ad66
--- /dev/null
+++ b/filterApis.js
@@ -0,0 +1,64 @@
+import * as path from "path";
+
+/**
+ * This is a pretty specific function.
+ * Given a list of filenames in a ./a/folder/filename-v23 format that may contain many filenames with different versions,
+ * it will return a list of filenames with only the highest version of each filename.
+ * For example, given
+ *
+ * ["../adyen-postman/postman/BinLookupService-v39.json",
+ * "../adyen-postman/postman/BinLookupService-v40.json",
+ * "../adyen-postman/postman/BinLookupService-v42.json",
+ * ["../adyen-postman/postman/CheckoutService-v70.json"]
+ *
+ * , the function will return
+ *
+ * ["../adyen-postman/postman/BinLookupService-v42.json",
+ * ["../adyen-postman/postman/CheckoutService-v70.json"]
+ *
+ * @constructor
+ * @param {Array.<string>} filenames a list of filenames, including path and extension
+ * @param {Array.<string>} filenames with only the highest version of each filename
+ */
+export function filenamesToSet(filenames){
+
+    const clearerApis = filenames.map((filename) => {
+        return {
+            "path" :filename,
+            "name" : path.parse(filename).name,
+            "root" : path.parse(filename).name.split("-")[0],
+            "version" : path.parse(filename).name.split("-v")[1],
+        }
+    });
+
+    const groupsOfApis = _groupBy(clearerApis, "root");
+    const highestVersions = Object.values(groupsOfApis).map((value) => {
+        return value.reduce(
+            (prev, current) => {
+                return prev.version > current.version ? prev : current
+            });
+    });
+
+    return highestVersions.map((value) => { return value.path});;
+}
+
+
+/**
+ * Group an array of objects using the given key
+ * @param {Array} xs an array of objects
+ * @param {String} key the key to group by
+ * @returns {Object} an object with each key being the value of the given key used to group by, and the value being an array of objects with that key
+ * @private
+ *
+ *  @example
+ *  // returns {"3": ["one", "two"], "5": ["three"]}
+ *  groupBy(['one', 'two', 'three'], 'length')
+ *
+ *  Thank you https://stackoverflow.com/questions/14446511/most-efficient-method-to-groupby-on-an-array-of-objects!
+ */
+function _groupBy(xs, key) {
+    return xs.reduce(function(rv, x) {
+        (rv[x[key]] = rv[x[key]] || []).push(x);
+        return rv;
+    }, {});
+}
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diff --git a/sort.js b/sort.js
deleted file mode 100644
index 075d356..0000000
--- a/sort.js
+++ /dev/null
@@ -1,3 +0,0 @@
-export function list(){
-    return [];
-}
\ No newline at end of file
diff --git a/tests/filterApis.js b/tests/filterApis.js
new file mode 100644
index 0000000..316ee4c
--- /dev/null
+++ b/tests/filterApis.js
@@ -0,0 +1,36 @@
+import { test } from 'uvu';
+import * as assert from 'uvu/assert';
+
+import {filenamesToSet} from '../filterApis.js';
+
+const FULL_LIST = "../adyen-postman/postman/BalanceControlService-v1.json ../adyen-postman/postman/BalancePlatformService-v1.json ../adyen-postman/postman/BalancePlatformService-v2.json ../adyen-postman/postman/BinLookupService-v40.json ../adyen-postman/postman/BinLookupService-v50.json ../adyen-postman/postman/BinLookupService-v52.json ../adyen-postman/postman/BinLookupService-v53.json ../adyen-postman/postman/BinLookupService-v54.json ../adyen-postman/postman/CheckoutService-v37.json ../adyen-postman/postman/CheckoutService-v40.json ../adyen-postman/postman/CheckoutService-v41.json ../adyen-postman/postman/CheckoutService-v46.json ../adyen-postman/postman/CheckoutService-v49.json ../adyen-postman/postman/CheckoutService-v50.json ../adyen-postman/postman/CheckoutService-v51.json ../adyen-postman/postman/CheckoutService-v52.json ../adyen-postman/postman/CheckoutService-v53.json ../adyen-postman/postman/CheckoutService-v64.json ../adyen-postman/postman/CheckoutService-v65.json ../adyen-postman/postman/CheckoutService-v66.json ../adyen-postman/postman/CheckoutService-v67.json ../adyen-postman/postman/CheckoutService-v68.json ../adyen-postman/postman/CheckoutService-v69.json ../adyen-postman/postman/CheckoutService-v70.json ../adyen-postman/postman/DataProtectionService-v1.json ../adyen-postman/postman/LegalEntityService-v1.json ../adyen-postman/postman/LegalEntityService-v2.json ../adyen-postman/postman/LegalEntityService-v3.json ../adyen-postman/postman/ManagementService-v1.json ../adyen-postman/postman/PayoutService-v30.json ../adyen-postman/postman/PayoutService-v40.json ../adyen-postman/postman/PayoutService-v50.json ../adyen-postman/postman/PayoutService-v51.json ../adyen-postman/postman/PayoutService-v52.json ../adyen-postman/postman/PayoutService-v64.json ../adyen-postman/postman/PayoutService-v67.json ../adyen-postman/postman/PayoutService-v68.json ../adyen-postman/postman/RecurringService-v25.json ../adyen-postman/postman/RecurringService-v30.json ../adyen-postman/postman/RecurringService-v40.json ../adyen-postman/postman/RecurringService-v49.json ../adyen-postman/postman/RecurringService-v67.json ../adyen-postman/postman/RecurringService-v68.json ../adyen-postman/postman/StoredValueService-v46.json ../adyen-postman/postman/TestCardService-v1.json ../adyen-postman/postman/TfmAPIService-v1.json ../adyen-postman/postman/TransferService-v1.json ../adyen-postman/postman/TransferService-v2.json ../adyen-postman/postman/TransferService-v3.json"
+const FULL_FILENAMES = FULL_LIST.split(" ");
+
+const CLEAN_LIST = "../adyen-postman/postman/BalanceControlService-v1.json ../adyen-postman/postman/BalancePlatformService-v2.json ../adyen-postman/postman/BinLookupService-v54.json ../adyen-postman/postman/CheckoutService-v70.json ../adyen-postman/postman/DataProtectionService-v1.json ../adyen-postman/postman/LegalEntityService-v3.json ../adyen-postman/postman/ManagementService-v1.json ../adyen-postman/postman/PayoutService-v68.json ../adyen-postman/postman/RecurringService-v68.json ../adyen-postman/postman/StoredValueService-v46.json ../adyen-postman/postman/TestCardService-v1.json ../adyen-postman/postman/TfmAPIService-v1.json ../adyen-postman/postman/TransferService-v3.json"
+const CLEAN_FILENAMES = CLEAN_LIST.split(" ");
+
+test('filenamesToSet empty', () => {
+    assert.equal(filenamesToSet([]), []);
+});
+
+test('filenamesToSet no reduction', () => {
+    assert.equal(filenamesToSet(
+        ["../adyen-postman/postman/BalanceControlService-v1.json", "../adyen-postman/postman/BinLookupService-v40.json"]
+    ),
+        ["../adyen-postman/postman/BalanceControlService-v1.json", "../adyen-postman/postman/BinLookupService-v40.json"]);
+});
+
+test('filenamesToSet simple, reduction', () => {
+    assert.equal(filenamesToSet(
+            ["../adyen-postman/postman/BinLookupService-v39.json", "../adyen-postman/postman/BinLookupService-v40.json", "../adyen-postman/postman/BinLookupService-v42.json"]
+        ),
+        ["../adyen-postman/postman/BinLookupService-v42.json"]);
+});
+
+test('filenamesToSet full', () => {
+    assert.equal(filenamesToSet(FULL_FILENAMES), CLEAN_FILENAMES);
+});
+
+test.run();
+
+
diff --git a/tests/sort.js b/tests/sort.js
deleted file mode 100644
index 946f136..0000000
--- a/tests/sort.js
+++ /dev/null
@@ -1,10 +0,0 @@
-import { test } from 'uvu';
-import * as assert from 'uvu/assert';
-
-import {list} from '../sort.js';
-test('sort.list', () => {
-    assert.equal(list(), []);
-});
-
-
-test.run();
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