A couple minor comments but nothing big.

There is one other minor thing that would probably be good but can be part of their own PR as it isn't pressing. I don't think we need to record this._metaNodesMap. The methods that use it could be rewritten to just use the client. For example, getMetaType could be rewritten to get the ID and then use getNode from the client. Checking if the node inherits from "Metadata" could also be checked by using a convenience method that walks up the inheritance tree and checks for a node that is both part of the meta and has the given name. This would likely be more performant than the current approach. Anyway, it isn't a huge deal so it doesn't need to be part of this PR.