Hard Dependency
a module cannot function without the other modules on which it depends
The module contains code that directly uses logic from another module (instances, class constants, static methods, public class properties, interfaces and traits).
The module contains strings that include class names, methods names, class constants, class properties, interfaces, and traits from another module.
The module de-serializes an object declared in another module.
The module uses or modifies the database tables used by another module.
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