Another type signature improvement?

Author: jmchilton

cwltool/main.py

@@ -21,6 +21,7 @@
 from schema_salad.sourceline import strip_dup_lineno
 
 from . import draft2tool, workflow
+from .builder import Builder
 from .cwlrdf import printdot, printrdf
 from .errors import UnsupportedRequirement, WorkflowException
 from .load_tool import fetch_document, make_tool, validate_document, jobloaderctx