- update to 1.13.1:
* Fixed :class:`.Rewriter` so that more than two instances
could be chained together correctly, also allowing multiple
``process_revision_directives`` callables to be chained.
* Fixed issue where the method
:meth:`.EnvironmentContext.get_x_argument` using the
:paramref:`.EnvironmentContext.get_x_argument.as_dictionary`
parameter would fail if an argument key were passed on the
command line as a name alone, that is, without an equal sign
``=`` or a value. Behavior is repaired where this condition is
detected and will return a blank string for the given key,
consistent with the behavior where the ``=`` sign is
present and no value.
* Fixed issue where the "unique" flag of an ``Index`` would not
be maintained when generating downgrade migrations.
* Fixed bug in versioning model where a downgrade across a
revision with two down revisions with one down revision
depending on the other, would produce an erroneous state in
the alembic_version table, making upgrades impossible
without manually repairing the table.
* Updated pep-484 typing to pass mypy "strict" mode, however
including per-module qualifications for specific typing
elements not yet complete.
* This allows us to catch specific typing issues that have been
ongoing such as import symbols not properly exported.