Unfortunately there is not, I can try to write some but do you have a more specific question?
The basic idea is that Python runs a webserver that serves several purposes:
- hosts the neuroglancer client
- provides a sockjs (similar to websocket) server used to synchronize/control the viewer json state, set up special Python-only configuration options like custom key and mouse bindings, request screenshots, and send credentials (e.g. for accessing Google cloud storage buckets)
- provides additional endpoints serving volumetric data, auto-generated meshes, and skeletons for in-memory python data sources (in python these correspond to LocalVolume and Skeletons piece, in the client these are python:// data sources).