Update default.py - Missing cosine_similarity transform for docs with Token Count 101–500 (#1934)

The `default_ transforms` function defined at
`src/ragas/testset/transforms/default.py` has a problem with handling
transforms for documents with 101-500 tokens.

The code divides the `transforms` configurations based on the document's
token count. Several transforms are instantiated when the ["101-500"
token count bins the first quartile
(Q1](https://github.com/explodinggradients/ragas/blob/2bc29a2b8358ddb6b167fdf7ab0518ad9371463c/src/ragas/testset/transforms/default.py#L128),
among them the `cosine_sim_builder`. While `cosine_sim_builder` is
correctly **instantiated** (line 139), it's then **not included** in the
list of transforms that are actually returned (line 153).

It appears that `cosine_sim_builder` was likely unintentionally omitted
from the returned transforms list. The intended behavior should probably
mirror how `ner_overlap_sim` is handled (line 120), where
`cosine_sim_builder` is instantiated and added to the returned list. The
current code effectively instantiates `cosine_sim_builder` but then
discards it. This omission might impact the number of relationships
created in the knowledge graph.

Author: rgrizzo-linksmt

src/ragas/testset/transforms/default.py

@@ -154,7 +154,7 @@ def filter_chunks(node):
             summary_extractor,
             node_filter,
             Parallel(summary_emb_extractor, theme_extractor, ner_extractor),
-            ner_overlap_sim,
+            Parallel(cosine_sim_builder, ner_overlap_sim),
         ]
     else:
         raise ValueError(