Minor doc fix.
Test for `defaultdict` clone access.
Remove deprecated `get_and_del_key`.
Allow a string as the `level` argument in `generate_password`.
Clarify that `no_instances` is not the negation of `are_instances`.
Deprecate xoutil.string.input.
Add support to use dateutil parser in records.
Extract isnull from check_nullable.
Jump to 1.6.7.
Release 1.6.7.
Merge branch 'release-1.6'