curl -i -X PUT "https://api.box.com/2.0/metadata_templates/enterprise/securityClassification-6VMVochwUWo/schema" \
     -H "authorization: Bearer <ACCESS_TOKEN>" \
     -H "content-type: application/json-patch+json" \
     -d '[{
       "op": "addEnumOption",
       "fieldKey": "Box__Security__Classification__Key",
       "data": {
         "key": "Sensitive",
         "staticConfig":{
          "classification": {
            "classificationDefinition": "Sensitive information that must not be shared.",
            "colorID": 4
            }
         }
       }
     }]'

List<MetadataTemplate.FieldOperation> updates = new ArrayList<MetadataTemplate.FieldOperation>();

String update = "{\n  op: \"addEnumOption\",\n  fieldKey: \"Box__Security__Classification__Key\",\n  data: {\n    key: \"Sensitive\"\n }\n}";

updates.add(new MetadataTemplate.FieldOperation(addCategoryFieldJSON));

MetadataTemplate.updateMetadataTemplate(api, Metadata.ENTERPRISE_METADATA_SCOPE, Metadata.CLASSIFICATION_TEMPLATE_KEY, updates);

template = client.metadata_template('enterprise', 'securityClassification-6VMVochwUWo')
new_updates = template.start_update()
new_updates.add_enum_option('Box__Security__Classification__Key', 'Sensitive')
updated_template = template.update_info(updates=new_updates)

var update = new BoxMetadataTemplateUpdate
{
    Op = MetadataTemplateUpdateOp.addEnumOption,
    FieldKey = "Box_Security_Classification_Key",
    Data = new
    {
        key = "Sensitive"
    }
};

var template = await client.MetadataManager
    .UpdateMetadataTemplate(new List<BoxMetadataTemplateUpdate>() { update }, "enterprise", "securityClassification-6VMVochwUWo");

var operations = [{
  op: "addEnumOption",
  fieldKey: "Box__Security__Classification__Key",
  data: {
    key: "Sensitive",
    classification: {
      classificationDefinition: "Sensitive information that must not be shared.",
      colorID: 4
    }
 }
}];
client.metadata.updateTemplate('enterprise', 'securityClassification-6VMVochwUWo', operations)
	.then(template => {
		// the updated classification template
	});