Issue when using DataSetProvider in a Morpheus Option Source Plugin

We are trying to build an option list source plugin for returning data for a multi-select option list using DataSetProvider as stated in the developer documentation:
However, the plugin is not getting detected by Morpheus even though we used the plugin API version as stated for the Morpheus version. There are no logs for error.
Is there any sample code for DataSetProvider plugin?

Morpheus Version: 6.2.2
Plugin API: 0.15.3