get module path and/or module id for module that called the plugin load

a.js

define(['loader!request'], function (someModule) {
    
});

gistfile1.txt

├── some-dir
│   ├── a.js
│   └── node_modules
│       ├── request

loader.js

define({
    load: function (name, req, onload, config) {
        // how do i get the path and/or module id for the module that is leveraging the plugin?
        // in the case module a.
    }
});