<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def get_columns_diff(changes):
 """Add the changed columns as a diff attribute. - changes: a list of changes (get_model_changes query.all()) Return: the same list, to which elements we added a "diff" attribute containing the changed columns. Diff defaults to []. """

    for change in changes:
        change.diff = []
        elt_changes = change.get_changes()
        if elt_changes:
            change.diff = elt_changes.columns

    return changes