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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 register(app_name, modules):
 """ simple module registering for later usage we don't want to import admin.py in models.py """

    global INSTALLED_APPS_REGISTER
    mod_list = INSTALLED_APPS_REGISTER.get(app_name, [])

    if isinstance(modules, basestring):
        mod_list.append(modules)
    elif is_iterable(modules):
        mod_list.extend(modules)

    INSTALLED_APPS_REGISTER[app_name] = mod_list