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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def get_hook_model():
 """ Returns the Custom Hook model if defined in settings, otherwise the default Hook model. """

    from rest_hooks.models import Hook
    HookModel = Hook
    if getattr(settings, 'HOOK_CUSTOM_MODEL', None):
        HookModel = get_module(settings.HOOK_CUSTOM_MODEL)
    return HookModel