expose innermost_child sampler

dimod/core/composite.py

@@ -45,6 +45,7 @@
     For more examples, see the source code for the composed
     documented in :ref:`quadratic_composites`.
 """
+
 import abc
 
 from dimod.core.sampler import Sampler
@@ -74,8 +75,12 @@ def child(self):
         except IndexError:
             raise RuntimeError("A Composite must have at least one child Sampler")
 
+    def innermost_child(self) -> Sampler:
+        """Returns the inner-most child sampler"""
+        return self.child.innermost_child()    
+
 
-class ComposedSampler(Sampler, Composite):
+class ComposedSampler(Composite, Sampler):
     """Abstract base class for dimod composed samplers.
 
     Inherits from :class:`.Sampler` and :class:`.Composite`.

dimod/core/sampler.py

@@ -105,6 +105,7 @@ def parameters(self):
             return self._parameters
 
 """
+from __future__ import annotations
 
 import abc
 import typing
@@ -317,3 +318,6 @@ def remove_unknown_kwargs(self, **kwargs) -> typing.Dict[str, typing.Any]:
             kwargs.pop(kw)
 
         return kwargs
+
+    def innermost_child(self) -> Sampler:
+            return self

tests/test_composite.py

@@ -39,3 +39,12 @@ def children(self):
         sampler = Dummy()
         with self.assertRaises(RuntimeError):
             sampler.child
+
+
+class TestInnermostChild(unittest.TestCase):
+
+    def test_composed_sampler(self):
+        innermost_child = dimod.ExactSolver()
+        sampler = dimod.ClipComposite(dimod.ScaleComposite(innermost_child))
+        self.assertTrue(sampler.innermost_child() is innermost_child)
+

tests/test_sampler.py

@@ -362,3 +362,7 @@ def properties(self):
 
         # Check that known kwargs are kept and unknown kwargs are removed
         self.assertDictEqual(kwargs, {'a': 1})
+
+    def test_innermost_child(self):
+        sampler = dimod.ExactSolver()
+        self.assertTrue(sampler.innermost_child() is sampler)