Following up on jupyterhub/binderhub#1017 (comment). In particular the comment about "reduce duplication".

A possible way to do that which I've seen in other projects is to add an endpoint to the backend from which the UI loads the config. We'd have an endpoint like binder.example.com/_config which returns a JSON which is then used to configure the dropdow

Describe the issue
In dark mode - hard to see three dots in node to open common props when not highlighted

To Reproduce
Steps to reproduce the behavior:
0. Activate dark mode,

1. Go to pipeline editor, drag a notebook to create a node
2. Scroll over the node and highlight the 3 dots.

Screenshots or log output
![image](https://user-images.githubusercontent.com/13340013/11038

Objective

Python 3.6 and above supports type hints and optional statically typing of Python code. Since its introduction is has seen a lot of adoption in many Python projects in particular in larger code bases. Type hints are completely optional and are stripped by the Python parser before runtime.

I am not the only one @plumerai anymore who li

Checks should be added to add_edges and add_nodes that the node/edge being added is actually a valid node/edge object and if not we should fail with a clear error message.

Originally posted by @ianhi in QuantStack/ipycytoscape#214 (comment)

cc @sven5s