Hi @11111 , the backends package is used to set up a context in which to draw objects in a Window , using either pyglet , pygame , or glfw . Each Backend class defines the core low-level functions required by a Window class, such as the ability to create an OpenGL context and flip the window.

The ‘.’ indicates a relative import - “A single dot means that the module or package referenced is in the same directory as the current location”. See absolute vs relative imports . In this instance, the window module imports the backends package using relative imports because the backends package is in the same directory as the window module, which contains the Window class used for drawing your stim etc.