added sample-functionality to sandwich operator when it is analytically possible

nifty4/operators/sandwich_operator.py

@@ -76,6 +76,12 @@ class SandwichOperator(EndomorphicOperator):
     def draw_sample(self, from_inverse=False, dtype=np.float64):
         # Inverse samples from general sandwiches is not possible
         if from_inverse:
+            if self._bun.capabilities & self._bun.INVERSE_TIMES:
+                try:
+                    s = self._cheese.draw_sample(from_inverse, dtype)
+                    return self._bun.inverse_times(s)
+                except:
+                    pass
             raise NotImplementedError(
                 "cannot draw from inverse of this operator")