Set n/a as placeholder
@@ -231,7 +231,7 @@ class Step(object):
c_data = {**c.entities, **{c.name: 1}}
for ent in ent_cols:
if ent not in c_data:
- c_data[ent] = None
+ c_data[ent] = 'n/a'
data.append(c_data)
data = pd.DataFrame.from_records(data)
