The FireWork class has been deprecated for awhile (replaced by Firework, which has a different capitalization). In FWS v1.2.4, the old capitalization is completely removed.
To adjust for this change:
Change any remaining instances of the “FireWork” class to “Firework”
Change any remaining instances of Workflow.from_FireWork() to Workflow.from_Firework()
The reason the old capitalization is being removed is to help distinguish at least a little better between “FireWorks” or “FWS” (the codebase) and “Firework” (the job class within the FWS software).