cleanup imports

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Author: keighrim

mmif/serialize/mmif.py

@@ -24,7 +24,7 @@
 from mmif.serialize.annotation import Annotation, Document
 from mmif.serialize.model import MmifObject, DataList
 from mmif.serialize.view import View
-from mmif.vocabulary import AnnotationTypes, DocumentTypes, DocumentTypesBase
+from mmif.vocabulary import AnnotationTypes, DocumentTypesBase
 
 __all__ = ['Mmif']