fix data bug - empty prep slot; replacing with underscore

qa_srl2018.py

@@ -54,7 +54,7 @@ SpanFeatureType = datasets.Sequence(datasets.Value("int32"), length=2)
 class QaSrl2018(datasets.GeneratorBasedBuilder):
     """QA-SRL2018: Large-Scale Question-Answer Driven Semantic Role Labeling corpus"""
 
-    VERSION = datasets.Version("1.0.2")
+    VERSION = datasets.Version("1.0.3")
 
     BUILDER_CONFIGS = [
         datasets.BuilderConfig(
@@ -138,7 +138,7 @@ class QaSrl2018(datasets.GeneratorBasedBuilder):
     def _generate_examples(self, filepath):
 
         """ Yields examples from a '.jsonl.gz' file ."""
-
+        empty_to_underscore = lambda s: "_" if s=="" else s
         with gzip.open(filepath, "rt") as f:
             qa_counter = 0
             for line in f:
@@ -158,7 +158,7 @@ class QaSrl2018(datasets.GeneratorBasedBuilder):
                             question_slots["subj"],                            
                             verb_surface,
                             question_slots["obj"],
-                            question_slots["prep"],
+                            empty_to_underscore(question_slots["prep"]), # fix bug in data
                             question_slots["obj2"],
                             '?'
                         ]