Formal verification cells
-------------------------

.. TODO:: Describe formal cells

   `$check`, `$assert`, `$assume`, `$live`, `$fair`, `$cover`, `$equiv`,
   `$initstate`, `$anyconst`, `$anyseq`, `$anyinit`, `$allconst`, and `$allseq`.

   Also `$ff` and `$_FF_` cells.

.. autocellgroup:: formal
   :members:
   :source:
   :linenos: