Can we Load a reusable WriteFile library file in test suite setup script and call the instance in as

Can we Load a reusable WriteFile library file in test suite setup script and call the instance of library file through context in test step assertion under that test suite.

As I when i am loading the library file in test suite setup script and calling it through context in test step script assertion then i am getting NULL object exception for the library.

But when i load the reusable WriteFile library file at test case setup script or directly in test step assertion through context then i am able to use that library.

Please let me know your thoughts on above query