added toXml function

lib/default.nix

@@ -0,0 +1,44 @@
+{nixpkgs, ...}:
+nixpkgs.lib.extend (
+  final: prev: {
+    toXMLGeneric = let
+      toXMLRecursive =
+        toXmlRecursive'
+        "<?xml version='1.0' encoding='utf-8'?>";
+
+      toXmlRecursive' = str: xml: let
+        parseTag = str: xml: (builtins.concatStringsSep "" [
+          str
+          "\n"
+          "<${xml.name}"
+
+          (
+            if (builtins.hasAttr "properties" xml)
+            then
+              (" "
+                + builtins.concatStringsSep " " (nixpkgs.lib.attrsets.mapAttrsToList
+                  (name: value: "${name}=\"${nixpkgs.lib.strings.escapeXML value}\"")
+                  xml.properties))
+            else ""
+          )
+
+          (
+            if builtins.hasAttr "content" xml
+            then ((toXmlRecursive' "" xml.content) + "\n</${xml.name}>")
+            else "/>"
+          )
+        ]);
+        output =
+          if (builtins.isAttrs xml)
+          then (parseTag str xml)
+          else if (builtins.isList xml)
+          then (builtins.concatStringsSep "\n" (builtins.map (x: (toXmlRecursive' "" x)) xml))
+          else if ((builtins.isBool xml) || (builtins.isInt xml) || (builtins.isNull xml) || (builtins.isFloat xml))
+          then (builtins.toString xml)
+          else nixpkgs.lib.abort "Cannot convert a ${builtins.typeOf xml} to XML";
+      in
+        output;
+    in
+      toXMLRecursive;
+  }
+)

lib/from_xml.nix

@@ -1,7 +0,0 @@
-{nixpkgs, ...}:
-nixpkgs.lib.extend (
-  final: prev: {
-    fromXml = {
-    };
-  }
-)