Looking for documentation on 'populate_list'

I've seen references to the 'populate_list' property in various discussion posts, such as here and here. From what I understand, it can be used to automatically fill in the value of a field with the value of a related field from a different module. But I have not been able to find any Sugar documentation on it. Am I missing something, or does the documentation of 'populate_list' really not exist?