Suspected memory leak

Hello, I am getting some behavior that makes me suspect there is a memory leak happening when removing and adding labels to a graph.

I have some code similar to the following:
```
[id] = MyApp.Server.get_by_label(label_val) # genserver callback w/ graph reducer
[label] = MyApp.Server.get_label(id) # wraps vertex_labels
new_label = Map.put(label,"foo",true) # update label
MyApp.Server.rm_label(id) # wraps remove_vertex_labels
MyApp.Server.add_label(id,new_label) # wraps label_vertex
```

This causes BEAM to run out of memory after a few hundred calls to this function.
Let me know if you'd like a self-running example or if theres any tracing/debugging I can do to get more info.