zenhack
Simplify IOPlugin.Data initialization
Remove the need to specify every component of Data. This introduces a new IOPlugin.PersistedData member which is the same as IOPlugin.Data, except that it is initialized with boolean False instead of None.
Also remove account_key and key from FullChainFile, it is not stored by
ChainFile. Replace a weird IOPlugin.EMPTY_DATA._replace(key=X) hack by
the more intuitive Data(key=X).
The __defaults__ construct is taken from
http://stackoverflow.com/a/18348004 and documented in
https://docs.python.org/2/reference/datamodel.html and
https://docs.python.org/3/reference/datamodel.html
Lekensteyn included the following code: https://github.com/kuba/simp_le/pull/63/commits
