update method
      
Future<CustomTemplate> 
update(
    
- CustomTemplate request,
- String path, {
- String? fingerprint,
- String? $fields,
Updates a GTM Template.
request - The metadata request object.
Request parameters:
path - GTM Custom Template's API relative path. Example:
accounts/{account_id}/containers/{container_id}/workspaces/{workspace_id}/templates/{template_id}
Value must have pattern
^accounts/\[^/\]+/containers/\[^/\]+/workspaces/\[^/\]+/templates/\[^/\]+$.
fingerprint - When provided, this fingerprint must match the fingerprint
of the templates in storage.
$fields - Selector specifying which fields to include in a partial
response.
Completes with a CustomTemplate.
Completes with a commons.ApiRequestError if the API endpoint returned an error.
If the used http.Client completes with an error when making a REST call,
this method will complete with the same error.
Implementation
async.Future<CustomTemplate> update(
  CustomTemplate request,
  core.String path, {
  core.String? fingerprint,
  core.String? $fields,
}) async {
  final body_ = convert.json.encode(request);
  final queryParams_ = <core.String, core.List<core.String>>{
    if (fingerprint != null) 'fingerprint': [fingerprint],
    if ($fields != null) 'fields': [$fields],
  };
  final url_ = 'tagmanager/v2/' + core.Uri.encodeFull('$path');
  final response_ = await _requester.request(
    url_,
    'PUT',
    body: body_,
    queryParams: queryParams_,
  );
  return CustomTemplate.fromJson(
      response_ as core.Map<core.String, core.dynamic>);
}