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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_prepopulated_value(field, instance):
 """ Returns preliminary value based on `populate_from`. """

    if hasattr(field.populate_from, '__call__'):
        # AutoSlugField(populate_from=lambda instance: ...)
        return field.populate_from(instance)
    else:
        # AutoSlugField(populate_from='foo')
        attr = getattr(instance, field.populate_from)
        return callable(attr) and attr() or attr