dict.__or__ (PEP-584)

There are a lot of ways to merge two dicts:

1. Long but simple:

   merged = d1.copy()
   merged.update(d2)
   

2. Unpacking:

   merged = {**d1, **d2}
   

3. Unpacking again (keys must be strings):

   merged = dict(d1, **d2)
   

4. collections.ChainMap. Result is not dict but so.

In python 3.9, PEP-584 introduced the 5th way. Meet the | operator for dict!

merged = d1 | d2

Basically, that is the same as the first way but shorter and can be inlined.