Upgrade pairwise implementation in tests to itertools (#287)

Author: nathanjmcdougall

tests/unit/application/graph/test_layers.py

@@ -83,7 +83,7 @@ def test_indirect_illegal_within_one_package(
         self, specify_container: bool, start: str, end: str, route_middle: list[str]
     ):
         graph = self._build_legal_graph()
-        import_pairs = _pairwise([start, *route_middle, end])
+        import_pairs = itertools.pairwise([start, *route_middle, end])
         for importer, imported in import_pairs:
             graph.add_import(importer=importer, imported=imported)
 
@@ -479,7 +479,7 @@ def test_indirect_illegal_within_one_package(
         self, specify_container: bool, start: str, end: str, route_middle: list[str]
     ):
         graph = self._build_legal_graph()
-        import_pairs = _pairwise([start, *route_middle, end])
+        import_pairs = itertools.pairwise([start, *route_middle, end])
         for importer, imported in import_pairs:
             graph.add_import(importer=importer, imported=imported)
 
@@ -668,7 +668,7 @@ def test_indirect_illegal_across_two_packages(
         self, start: str, end: str, route_middle: list[str]
     ):
         graph = self._build_legal_graph()
-        import_pairs = _pairwise([start, *route_middle, end])
+        import_pairs = itertools.pairwise([start, *route_middle, end])
         for importer, imported in import_pairs:
             graph.add_import(importer=importer, imported=imported)
 
@@ -949,18 +949,6 @@ def test_missing_layer_is_ignored_with_multiple_containers(self):
         }
 
 
-def _pairwise(iterable):
-    """
-    Return successive overlapping pairs taken from the input iterable.
-    pairwise('ABCDEFG') --> AB BC CD DE EF FG
-
-    TODO: Replace with itertools.pairwise once on Python 3.10.
-    """
-    a, b = itertools.tee(iterable)
-    next(b, None)
-    return zip(a, b)
-
-
 class TestClosedLayers:
     @pytest.mark.parametrize(
         "importer, imported, expect_ok",