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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_invitation_model():
 """ Returns the Invitation model that is active in this project. """

    path = app_settings.INVITATION_MODEL
    try:
        return django_apps.get_model(path)
    except ValueError:
        raise ImproperlyConfigured(
            "path must be of the form 'app_label.model_name'"
        )
    except LookupError:
        raise ImproperlyConfigured(
            "path refers to model '%s' that\
             has not been installed" % app_settings.INVITATION_MODEL
        )