Hello, there (specially @spiffyjr)!

When I want to use the plugin view helper of Zend framework in a particular twig view file, it says:
Unknown "plugin" function in "{particular-view-template}" at line {line-number}.
It occurs when I want to use the plugin view helper as {% set formLabel = plugin('formLabel') %}.

Now, please help me to understand how I can use this plugin view helper.
Thanks, in advance.