Oops, I should have commented it. Here I'm assuming the set functions are named the same way as the attributes themselves. For  example, the bridge DTO has functions called `name()` and `admin_state_up()`, which correspond to the attribute names `name` and `admin_state_up`. So, I'm using `getattr()` to fetch the set function corresponding to that attribute/field and then I'm applying it to the attribute's new value (`fields[field_name]`).