feat: Add Spell Correction Spec to Google Cloud Enterprise Search connector (#8705)

libs/langchain/langchain/retrievers/google_cloud_enterprise_search.py

@@ -56,6 +56,16 @@ class GoogleCloudEnterpriseSearchRetriever(BaseRetriever):
         SearchResponse.total_size is zero.
     2 - Automatic query expansion built by the Search API.
     """
+    spell_correction_mode: int = Field(default=2, ge=0, le=2)
+    """Specification to determine under which conditions query expansion should occur.
+    0 - Unspecified spell correction mode. In this case, server behavior defaults 
+        to auto.
+    1 - Suggestion only. Search API will try to find a spell suggestion if there is any
+        and put in the `SearchResponse.corrected_query`.
+        The spell suggestion will not be used as the search query.
+    2 - Automatic spell correction built by the Search API.
+        Search will be based on the corrected query if found.
+    """
     credentials: Any = None
     """The default custom credentials (google.auth.credentials.Credentials) to use
     when making API calls. If not provided, credentials will be ascertained from
@@ -134,6 +144,10 @@ class GoogleCloudEnterpriseSearchRetriever(BaseRetriever):
             condition=self.query_expansion_condition,
         )
 
+        spell_correction_spec = SearchRequest.SpellCorrectionSpec(
+            mode=self.spell_correction_mode
+        )
+
         if self.get_extractive_answers:
             extractive_content_spec = (
                 SearchRequest.ContentSearchSpec.ExtractiveContentSpec(
@@ -158,6 +172,7 @@ class GoogleCloudEnterpriseSearchRetriever(BaseRetriever):
             page_size=self.max_documents,
             content_search_spec=content_search_spec,
             query_expansion_spec=query_expansion_spec,
+            spell_correction_spec=spell_correction_spec,
         )
 
     def _get_relevant_documents(