Python API Docs: add non-invert Bone.convert_local_to_pose example.

This updates the example function to support assigning a subset of
bone matrices. The code was tested to work in real use by @gaiaclary.

doc/python_api/examples/bpy.types.Bone.convert_local_to_pose.py

@@ -8,6 +8,7 @@ def set_pose_matrices(obj, matrix_map):
     "Assign pose space matrices of all bones at once, ignoring constraints."
 
     def rec(pbone, parent_matrix):
+        if pbone.name in matrix_map:
             matrix = matrix_map[pbone.name]
 
             ## Instead of:
@@ -29,6 +30,20 @@ def set_pose_matrices(obj, matrix_map):
                     pbone.bone.matrix_local,
                     invert=True
                 )
+        else:
+            # Compute the updated pose matrix from local and new parent matrix
+            if pbone.parent:
+                matrix = pbone.bone.convert_local_to_pose(
+                    pbone.matrix_basis,
+                    pbone.bone.matrix_local,
+                    parent_matrix=parent_matrix,
+                    parent_matrix_local=pbone.parent.bone.matrix_local,
+                )
+            else:
+                matrix = pbone.bone.convert_local_to_pose(
+                    pbone.matrix_basis,
+                    pbone.bone.matrix_local,
+                )
 
         # Recursively process children, passing the new matrix through
         for child in pbone.children: