- The check command checks to see if there is anything missing from the
specified output file.
- All types in the `_ast' module are also exported from the `ast'
module, so there is no need to use `_ast' explicitly.
- Don't raise an exception when a value from the specification doesn't
match a predicate, the `check' command will take care of this.
- Place some functions outside of their previous classes. These are used
by several classes/methods and they need no state from these classes.
