Add deprecation warnings for 2D classes

lib/matplotlib/transforms.py

@@ -1924,6 +1924,12 @@ def inverted(self):
         return self._inverted
 
 
+@_api.deprecated("3.9", alternative="AffineImmutable")
+class Affine2DBase(AffineImmutable):
+    def __init__(self, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+
+
 def _affine_factory(mtx, dims, *args, **kwargs):
     if dims == 2:
         return Affine2D(mtx, *args, **kwargs)
@@ -2396,6 +2402,12 @@ def get_matrix(self):
         return self._mtx
 
 
+@_api.deprecated("3.9", alternative="BlendedAffine")
+class BlendedAffine2D(BlendedAffine):
+    def __init__(self, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+
+
 def blended_transform_factory(*args):
     """
     Create a new "blended" transform using *x_transform* to transform
@@ -2567,6 +2579,12 @@ def get_matrix(self):
         return self._mtx
 
 
+@_api.deprecated("3.9", alternative="CompositeAffine")
+class CompositeAffine2D(CompositeAffine):
+    def __init__(self, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+
+
 def composite_transform_factory(a, b):
     """
     Create a new composite transform that is the result of applying