Hi Cdb experts. Thanks as always for your help.

I am trying to write down a vector field as is common in differential geometry, with a basis of derivatives. For example:

`u := u^{\mu} \partial_{\mu};`

My difficulty is that any serious calculation I try to do comes out all zeros. For example,

```
from cdb.relativity.abstract import *
u := u^{\mu} \partial_{\mu};
v := v^{\mu} \partial_{\mu};
ex := @(u)@(v) - @(v)@(u);
```

Is there any way to make cdb aware that should be considered on operator "waiting" for something to operate upon?

Thank you!

GPN