Merge pull request #401 from github/python_pairs

Adds pairs

languages/tree-sitter-stack-graphs-python/src/stack-graphs.tsg

@@ -152,6 +152,7 @@ attribute node_symbol = node            => symbol = (source-text node), source_n
   (set)
   (set_comprehension)
   (tuple)
+  (pair)
   (parenthesized_expression)
   (generator_expression)
   (ellipsis)