fixed bug in optional parameter name concatenation

src/dbispipeline/analytics.py

@@ -213,13 +213,13 @@ def _read_parameters(dictionary, prefix='', use_prefix=True):
         if k == 'selected_model':
             k = prefix + k if use_prefix else k
             result[k] = str(v[0])
-            result.update(_read_parameters(v[1], v[0] + '__'))
+            result.update(_read_parameters(v[1], str(v[0]) + '__'))
         # PipelineHelper is somewhere else
         elif '__selected_model' in k:
             # the [:-16] cuts off the string '__selected_model'
             key_name = prefix + k[:-16] if use_prefix else k[:-16]
             result[key_name] = str(v[0])
-            result.update(_read_parameters(v[1], v[0] + '__'))
+            result.update(_read_parameters(v[1], str(v[0]) + '__'))
         # "Regular" GridSearch element
         else:
             key_name = prefix + k if use_prefix else k