community[patch]: Pass kwargs to SPARQLStore from RdfGraph (#20385)

This introduces `store_kwargs` which behaves similarly to `graph_kwargs`
on the `RdfGraph` object, which will enable users to pass `headers` and
other arguments to the underlying `SPARQLStore` object. I have also made
a [PR in `rdflib` to support passing
`default_graph`](https://github.com/RDFLib/rdflib/pull/2761).

Example usage:
```python
from langchain_community.graphs import RdfGraph

graph = RdfGraph(
    query_endpoint="http://localhost/sparql",
    standard="rdf",
    store_kwargs=dict(
        default_graph="http://example.com/mygraph"
    )
)
```

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---------

Co-authored-by: Bagatur <22008038+baskaryan@users.noreply.github.com>
Co-authored-by: Bagatur <baskaryan@gmail.com>

libs/community/langchain_community/graphs/rdf_graph.py

@@ -117,6 +117,7 @@ class RdfGraph:
         standard: Optional[str] = "rdf",
         local_copy: Optional[str] = None,
         graph_kwargs: Optional[Dict] = None,
+        store_kwargs: Optional[Dict] = None,
     ) -> None:
         """
         Set up the RDFlib graph
@@ -130,6 +131,9 @@ class RdfGraph:
         :param graph_kwargs: Additional rdflib.Graph specific kwargs
         that will be used to initialize it,
         if query_endpoint is provided.
+        :param store_kwargs: Additional sparqlstore.SPARQLStore specific kwargs
+        that will be used to initialize it,
+        if query_endpoint is provided.
         """
         self.source_file = source_file
         self.serialization = serialization
@@ -174,12 +178,13 @@ class RdfGraph:
             self.graph.parse(source_file, format=self.serialization)
 
         if query_endpoint:
+            store_kwargs = store_kwargs or {}
             self.mode = "store"
             if not update_endpoint:
-                self._store = sparqlstore.SPARQLStore()
+                self._store = sparqlstore.SPARQLStore(**store_kwargs)
                 self._store.open(query_endpoint)
             else:
-                self._store = sparqlstore.SPARQLUpdateStore()
+                self._store = sparqlstore.SPARQLUpdateStore(**store_kwargs)
                 self._store.open((query_endpoint, update_endpoint))
             graph_kwargs = graph_kwargs or {}
             self.graph = rdflib.Graph(self._store, **graph_kwargs)