added example for xml handling

Author: mqnifestkelvin

examples/document.py

@@ -2,6 +2,7 @@
 from modelspec import field, instance_of, optional
 from modelspec.base_types import Base
 from typing import List
+from modelspec.utils import save_to_xml_file
 
 # Example showing how to create a model of a document and use it to create/serialize instances
 
@@ -70,10 +71,12 @@ class Document(Base):
 doc.to_json_file("document.json")
 doc.to_yaml_file("document.yaml")
 doc.to_bson_file("document.bson")
+doc.to_xml_file("document.xml")
 
 print(" >> Full document details in YAML format:\n")
 
 print(doc.to_yaml())
+print(doc.to_xml())
 
 doc_md = doc.generate_documentation(format="markdown")
 
@@ -106,3 +109,5 @@ class Document(Base):
 
 with open("document.specification.bson", "wb") as d:
     d.write(bson.encode(doc_dict))
+
+save_to_xml_file(doc_dict,"document.specification.xml")