| Remove the tri-state parameter "hash", and add the boolean "unsafe_hash". If | |
| unsafe_hash is True, add a __hash__ function, but if a __hash__ exists, | |
| raise TypeError. If unsafe_hash is False, add a __hash__ based on the | |
| values of eq= and frozen=. The unsafe_hash=False behavior is the same as | |
| the old hash=None behavior. unsafe_hash=False is the default, just as | |
| hash=None used to be. |