But this would change the behavior since Idx is now Atom, which means I could just as well just delete the ```elif isinstance(expr, Idx):``` case if I move ```elif expr.is_Atom:``` up.

Moving the line yields this test error:
```
__________________________________________________________________________ sympy/tensor/tests/test_index_methods.py:test_get_indices_Idx ___________________________________________________________________________
  File "/home/bjorn/vc/sympy/sympy/tensor/tests/test_index_methods.py", line 30, in test_get_indices_Idx
    assert get_indices(f(i)*j) == (set([i, j]), {})
AssertionError

```