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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 _callback_factory(callback_imp):
 """Factory for creating a is authenticated callback."""

    if callback_imp is None:
        try:
            pkg_resources.get_distribution('flask-login')
            from flask_login import current_user
            return lambda: current_user.is_authenticated
        except pkg_resources.DistributionNotFound:
            return lambda: False
    elif isinstance(callback_imp, string_types):
        return import_string(callback_imp)
    else:
        return callback_imp