cascade with drop_table
ahh looks like you just fixed it in 3.0.9
https://github.com/coleifer/peewee/commit/d49784c2d6e525d882aab702fe0d2cf8163e4c18

will see if i can grab that hmm, tried 3.0.9 and even took what is in git, still get unexpected keyword.  Though looks like it should work ...  Let me look into it some more. Fixed.
Porting up from 2 to 3 looking for cascade option

.db.database.drop_tables(ALL_MODELS, safe=True, cascade=True)
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/peewee.py", line 2579, in drop_tables
    model.drop_table(**kwargs)
TypeError: drop_table() got an unexpected keyword argument 'cascade'