Put the chain.py file and chain.pyi (for auto completion) to your project.
from chain import chain, it
chain(range(10)).map(it * 2).filter(it > 3).to_list()
If you're a pythonic man, you dislike this library and write:
[t for i in range(10) if (t := i * 2) > 3]
Wow, so pythonic, but not me!
MIT @ hyrious