disable generation of filter argument for lists of union types (closes issue #113)

Author: keski

graphql-api-generator/utils/utils.py

@@ -650,7 +650,7 @@ def add_object_type_filters(schema: GraphQLSchema):
                 continue
 
             named_type = get_named_type(field.type)
-            if is_enum_or_scalar(named_type):
+            if is_enum_or_scalar(named_type) or is_union_type(named_type):
                 continue
 
             if field_name.startswith('_incoming') or field_name.startswith('_outgoing'):