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This indicates that the code depends upon a class called Course which is defined in the file js/models/course.js. 

See RequireJS at edX for more details.

Underscore Templates

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    ... = _.template($("#show-textbook-tpl").text(...));

 The The above code reads the text out of the element with the specified name. Via naming convention, it indicates that you will find the template in a file named show-textbook.underscore.

 Newer Newer code uses the RequireJS.text library to manage the JavaScript dependencies. You may see code like the following:

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