Proper way to copy an object

When using glyphsLib and attempting to use .copy() as I would in Glyphs App, I get the error that `there is no attribute 'copy'`

I have tried importing copy and then using `copy.copy()`, but this yields unexpected behavior. when doing something like:
```
newMaster = copy.copy(font.masters[0])
newMaster.name = "New Master"
font.masters.append(newMaster)
```

The name of the copied master changes to whatever newMaster.name is set to. Essentially no new master is added and instead `font.masters[0]` is renamed.

I am assuming that I am approaching this the wrong way or just missing something, what is the proper way to accomplish this?

Start by tracing the glyphsLib object behind font.masters[0] and how its nested data is copied. Reproduce the shown snippet, then verify that the copied master can be renamed and appended without changing the original or sharing mutable state.

Written by the indexing model from the issue text.